Wireless energy transfer modeling tool

ABSTRACT

A method includes defining and storing one or more attributes of a source resonator and a device resonator forming a system, defining and storing the interaction between the source resonator and the device resonator, modeling the electromagnetic performance of the system to derive one or more modeled values and utilizing the derived one or more modeled values to design an impedance matching network.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §120, this application is a continuation of andclaims priority to U.S. patent application Ser. No. 13/668,756, filed onNov. 5, 2012, which claims the benefit of U.S. provisional patentapplication 61/555,941 filed Nov. 4, 2011. The contents of the priorapplications are incorporated herein by reference in their entirety.

BACKGROUND

1. Field

This disclosure relates to wireless energy transfer, methods, systemsand apparati to accomplish such transfer, and applications.

2. Description of the Related Art

Energy distribution over an area to moving devices or devices that maybe often repositioned is unpractical with wired connections. Moving andchanging devices create the possibility of wire tangles, trippinghazards, and the like. Wireless energy transfer over a larger area maybe difficult when the area or region in which devices may be present maybe large compared to the size of the device. Large mismatches in asource and device wireless energy capture modules may pose challenges indelivering enough energy to the devices at a high enough efficiency tomake the implementations practical or may be difficult to deploy.

Therefore a need exists for methods and designs for energy distributionthat is wire free but easy to deploy and configurable while may deliversufficient power to be practical to power many household and industrialdevices.

SUMMARY

Resonators and resonator assemblies may be positioned to distributewireless energy over a larger area in packaging applications. Thewireless energy transfer resonators and components that may be used havebeen described in, for example, in commonly owned U.S. patentapplication Ser. No. 12/789,611 published on Sep. 23, 2010 as U.S. Pat.Pub. No. 2010/0237709 and entitled “RESONATOR ARRAYS FOR WIRELESS ENERGYTRANSFER,” and U.S. patent application Ser. No. 12/722,050 published onJul. 22, 2010 as U.S. Pat. Pub. No. 2010/0181843 and entitled “WIRELESSENERGY TRANSFER FOR REFRIGERATOR APPLICATION” the contents of which areincorporated in their entirety as if fully set forth herein.

In accordance with an exemplary and non-limiting embodiment, a methodcomprises defining and storing one or more attributes of a sourceresonator and a device resonator forming a system, defining and storingthe interaction between the source resonator and the device resonator,modeling the electromagnetic performance of the system to derive one ormore modeled values and utilizing the derived one or more modeled valuesto design an impedance matching network.

In accordance with another exemplary and non-limiting embodiment, anon-transitory computer-readable medium contains a set of instructionsthat causes a computer to enable the defining of one or more attributesof a source resonator and a device resonator forming a system, enablethe defining of an interaction between the source resonator and thedevice resonator, model the electromagnetic performance of the system toderive one or more modeled values and utilize the derived one or moremodeled values to design an impedance matching network.

Unless otherwise indicated, this disclosure uses the terms wirelessenergy transfer, wireless power transfer, wireless power transmission,and the like, interchangeably. Those skilled in the art will understandthat a variety of system architectures may be supported by the widerange of wireless system designs and functionalities described in thisapplication.

This disclosure references certain individual circuit components andelements such as capacitors, inductors, resistors, diodes, transformers,switches and the like; combinations of these elements as networks,topologies, circuits, and the like; and objects that have inherentcharacteristics such as “self-resonant” objects with capacitance orinductance distributed (or partially distributed, as opposed to solelylumped) throughout the entire object. It would be understood by one ofordinary skill in the art that adjusting and controlling variablecomponents within a circuit or network may adjust the performance ofthat circuit or network and that those adjustments may be describedgenerally as tuning, adjusting, matching, correcting, and the like.Other methods to tune or adjust the operating point of the wirelesspower transfer system may be used alone, or in addition to adjustingtunable components such as inductors and capacitors, or banks ofinductors and capacitors. Those skilled in the art will recognize that aparticular topology discussed in this disclosure can be implemented in avariety of other ways.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. In case of conflict withpublications, patent applications, patents, and other referencesmentioned or incorporated herein by reference, the presentspecification, including definitions, will control.

Any of the features described above may be used, alone or incombination, without departing from the scope of this disclosure. Otherfeatures, objects, and advantages of the systems and methods disclosedherein will be apparent from the following detailed description andfigures.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a system block diagram of wireless energy transferconfigurations.

FIGS. 2A-2F are exemplary structures and schematics of simple resonatorstructures.

FIG. 3 is a block diagram of a wireless source with a single-endedamplifier.

FIG. 4 is a block diagram of a wireless source with a differentialamplifier.

FIGS. 5A and 5B are block diagrams of sensing circuits.

FIGS. 6A, 6B, and 6C are block diagrams of a wireless source.

FIG. 7 is a plot showing the effects of a duty cycle on the parametersof an amplifier.

FIG. 8 is a simplified circuit diagram of a wireless power source with aswitching amplifier.

FIG. 9 shows plots of the effects of changes of parameters of a wirelesspower source.

FIG. 10 shows plots of the effects of changes of parameters of awireless power source.

FIGS. 11A, 11B, 11C, and 11D are plots showing the effects of changes ofparameters of a wireless power source.

FIG. 12 shows plots of the effects of changes of parameters of awireless power source.

FIG. 13 is a simplified circuit diagram of a wireless energy transfersystem comprising a wireless power source with a switching amplifier anda wireless power device.

FIG. 14 shows plots of the effects of changes of parameters of awireless power source.

FIG. 15 is a diagram of a resonator showing possible non-uniformmagnetic field distributions due to irregular spacing between tiles ofmagnetic material.

FIG. 16 is a resonator with an arrangement of tiles in a block ofmagnetic material that may reduce hotspots in the magnetic materialblock.

FIG. 17A is a resonator with a block of magnetic material comprisingsmaller individual tiles and 17B and 17C is the resonator withadditional strips of thermally conductive material used for thermalmanagement.

FIG. 18 is a diagram of communication and energy transfer in amultisource system.

FIG. 19A and FIG. 19B are diagrams showing a method for energyverification.

FIG. 20 is a diagram of a solar PV panel with several integratedresonators.

FIG. 21 is a diagram of a solar PV panel with an external resonatorattached by a cable.

FIG. 22 is a diagram of a vehicle with solar PV panels with wirelesspower transfer.

FIG. 23 is a diagram of a sun umbrella with solar PV panels withwireless power resonators that can provide power to devices under theumbrella.

FIG. 24 is a diagram of an embodiment of rooftop solar PV panels withwireless power transfer.

FIG. 25 is a diagram of a rooftop solar PV panel system with independentresonators.

FIG. 26 is a diagram of a rooftop solar PV panel system with wirelesspower transfer between panels.

FIG. 27 is a diagram of a rooftop solar PV panel system with aconnecting strip that wirelessly transfers power from several solar PVpanels to one resonator.

FIG. 28A shows a circuit model for a series of PV panels and FIG. 28Bshows typical PV panel operating characteristics.

FIG. 29 shows a plot of array voltage versus array current.

FIG. 30 shows PV panel resistance and current characteristics.

FIGS. 31A-31C shows block diagrams of wireless energy transfer systemsadapted for a PV panel.

FIG. 32 is a diagram showing multiple outputs of panels combinedtogether.

FIG. 33 is diagram of a wireless energy transfer system with PV panels.

FIG. 34 is diagram of an amplifier for wireless energy transfer systemwith PV panels.

FIGS. 35A and 35B shows voltage and current diagrams during operation ofan amplifier.

FIG. 36 shows characteristics of the impedance of the wireless source.

FIGS. 37A and 37B shows characteristics of the impedance of the wirelesssource.

FIG. 38 shows a wireless energy transfer source with a PV cell.

FIG. 39 shows a procedure for tuning the source for use with a PV panel.

FIG. 40 shows a diagram of a wireless energy transfer system with a PVpanels.

FIG. 40 shows a diagram of a wireless energy transfer system with a PVpanels.

FIG. 41 shows a diagram of a wireless energy transfer system with a PVpanels.

FIG. 42 is diagram of a packaging enabled with wireless energy transfer.

FIG. 43 is diagram of a packaging enabled with wireless energy transfer.

FIG. 44 is diagram of a stack of packages enabled with wireless energytransfer.

FIG. 45 is diagram of a packaging enabled with wireless energy transferwith a detuning patch.

FIG. 46 is diagram of a packaging enabled with wireless energy transfer.

FIG. 47 is a flow chart of a method according to an exemplary andnon-limiting embodiment.

FIG. 48 is an illustration of a user interface for entering source coildesign parameters according to an exemplary and non-limiting embodiment.

FIG. 49 is an illustration of a user interface for selecting source coildesigns according to an exemplary and non-limiting embodiment.

FIG. 50 is an illustration of a user interface for entering device coildesign parameters according to an exemplary and non-limiting embodiment.

FIG. 51 is an illustration of a user interface for entering source coiland device coil position parameters according to an exemplary andnon-limiting embodiment.

FIG. 52 is an illustration of an error message according to an exemplaryand non-limiting embodiment.

FIG. 53 is an illustration of an error message according to an exemplaryand non-limiting embodiment.

FIG. 54 is an illustration of an error message according to an exemplaryand non-limiting embodiment.

FIG. 55 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 56 is a flow chart of a method according to an exemplary andnon-limiting embodiment.

FIG. 57 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 58 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 59 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 60 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 61 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 62 is an illustration of a user interface according to an exemplaryand non-limiting embodiment.

FIG. 63 is an illustration of an exemplary system according to anexemplary and non-limiting embodiment.

FIG. 64 is a flow chart of a method according to an exemplary andnon-limiting embodiment.

DETAILED DESCRIPTION

As described above, this disclosure relates to wireless energy transferusing coupled electromagnetic resonators. However, such energy transferis not restricted to electromagnetic resonators, and the wireless energytransfer systems described herein are more general and may beimplemented using a wide variety of resonators and resonant objects.

As those skilled in the art will recognize, important considerations forresonator-based power transfer include resonator efficiency andresonator coupling. Extensive discussion of such issues, e.g., coupledmode theory (CMT), coupling coefficients and factors, quality factors(also referred to as Q-factors), and impedance matching is provided, forexample, in U.S. patent application Ser. No. 12/789,611 published onSep. 23, 2010 as US 20100237709 and entitled “RESONATOR ARRAYS FORWIRELESS ENERGY TRANSFER,” and U.S. patent application Ser. No.12/722,050 published on Jul. 22, 2010 as US 20100181843 and entitled“WIRELESS ENERGY TRANSFER FOR REFRIGERATOR APPLICATION” and incorporatedherein by reference in its entirety as if fully set forth herein.

A resonator may be defined as a resonant structure that can store energyin at least two different forms, and where the stored energy oscillatesbetween the two forms. The resonant structure will have a specificoscillation mode with a resonant (modal) frequency, f, and a resonant(modal) field. The angular resonant frequency, ω, may be defined asω=2πf, the resonant period, T, may be defined as T=1/f=2π/ω, and theresonant wavelength, λ, may be defined as λ=c/f, where c is the speed ofthe associated field waves (light, for electromagnetic resonators). Inthe absence of loss mechanisms, coupling mechanisms or external energysupplying or draining mechanisms, the total amount of energy stored bythe resonator, W, would stay fixed, but the form of the energy wouldoscillate between the two forms supported by the resonator, wherein oneform would be maximum when the other is minimum and vice versa.

For example, a resonator may be constructed such that the two forms ofstored energy are magnetic energy and electric energy. Further, theresonator may be constructed such that the electric energy stored by theelectric field is primarily confined within the structure while themagnetic energy stored by the magnetic field is primarily in the regionsurrounding the resonator. In other words, the total electric andmagnetic energies would be equal, but their localization would bedifferent. Using such structures, energy exchange between at least twostructures may be mediated by the resonant magnetic near-field of the atleast two resonators. These types of resonators may be referred to asmagnetic resonators.

An important parameter of resonators used in wireless power transmissionsystems is the Quality Factor, or Q-factor, or Q, of the resonator,which characterizes the energy decay and is inversely proportional toenergy losses of the resonator. It may be defined as Q=ω*W/P, where P isthe time-averaged power lost at steady state. That is, a resonator witha high-Q has relatively low intrinsic losses and can store energy for arelatively long time. Since the resonator loses energy at its intrinsicdecay rate, 2Γ, its Q, also referred to as its intrinsic Q, is given byQ=ω/2Γ. The quality factor also represents the number of oscillationperiods, T, it takes for the energy in the resonator to decay by afactor of e^(−2π). Note that the quality factor or intrinsic qualityfactor or Q of the resonator is that due only to intrinsic lossmechanisms. The Q of a resonator connected to, or coupled to a powergenerator, g, or load, l, may be called the “loaded quality factor” orthe “loaded Q”. The Q of a resonator in the presence of an extraneousobject that is not intended to be part of the energy transfer system maybe called the “perturbed quality factor” or the “perturbed Q”.

Resonators, coupled through any portion of their near-fields mayinteract and exchange energy. The efficiency of this energy transfer canbe significantly enhanced if the resonators operate at substantially thesame resonant frequency. By way of example, but not limitation, imaginea source resonator with Q_(s), and a device resonator with Q_(d). High-Qwireless energy transfer systems may utilize resonators that are high-Q.The Q of each resonator may be high. The geometric mean of the resonatorQ's, √{square root over (Q_(s)Q_(d))} may also or instead be high.

The coupling factor, k, is a number between 0≦|k|≦1, and it may beindependent (or nearly independent) of the resonant frequencies of thesource and device resonators, when those are placed at sub-wavelengthdistances. Rather the coupling factor k may be determined mostly by therelative geometry and the distance between the source and deviceresonators where the physical decay-law of the field mediating theircoupling is taken into account. The coupling coefficient used in CMT,κ=k√{square root over (ω_(s)ω_(d))}/2, may be a strong function of theresonant frequencies, as well as other properties of the resonatorstructures. In applications for wireless energy transfer utilizing thenear-fields of the resonators, it is desirable to have the size of theresonator be much smaller than the resonant wavelength, so that powerlost by radiation is reduced. In some embodiments, high-Q resonators aresub-wavelength structures. In some electromagnetic embodiments, high-Qresonator structures are designed to have resonant frequencies higherthan 100 kHz. In other embodiments, the resonant frequencies may be lessthan 1 GHz.

In exemplary embodiments, the power radiated into the far-field by thesesub wavelength resonators may be further reduced by lowering theresonant frequency of the resonators and the operating frequency of thesystem. In other embodiments, the far field radiation may be reduced byarranging for the far fields of two or more resonators to interferedestructively in the far field.

In a wireless energy transfer system a resonator may be used as awireless energy source, a wireless energy capture device, a repeater ora combination thereof. In embodiments a resonator may alternate betweentransferring energy, receiving energy or relaying energy. In a wirelessenergy transfer system one or more magnetic resonators may be coupled toan energy source and be energized to produce an oscillating magneticnear-field. Other resonators that are within the oscillating magneticnear-fields may capture these fields and convert the energy intoelectrical energy that may be used to power or charge a load therebyenabling wireless transfer of useful energy.

The so-called “useful” energy in a useful energy exchange is the energyor power that must be delivered to a device in order to power or chargeit at an acceptable rate. The transfer efficiency that corresponds to auseful energy exchange may be system or application-dependent. Forexample, high power vehicle charging applications that transferkilowatts of power may need to be at least 80% efficient in order tosupply useful amounts of power resulting in a useful energy exchangesufficient to recharge a vehicle battery without significantly heatingup various components of the transfer system. In some consumerelectronics applications, a useful energy exchange may include anyenergy transfer efficiencies greater than 10%, or any other amountacceptable to keep rechargeable batteries “topped off” and running forlong periods of time. In implanted medical device applications, a usefulenergy exchange may be any exchange that does not harm the patient butthat extends the life of a battery or wakes up a sensor or monitor orstimulator. In such applications, 100 mW of power or less may be useful.In distributed sensing applications, power transfer of microwatts may beuseful, and transfer efficiencies may be well below 1%.

A useful energy exchange for wireless energy transfer in a powering orrecharging application may be efficient, highly efficient, or efficientenough, as long as the wasted energy levels, heat dissipation, andassociated field strengths are within tolerable limits and are balancedappropriately with related factors such as cost, weight, size, and thelike.

The resonators may be referred to as source resonators, deviceresonators, first resonators, second resonators, repeater resonators,and the like. Implementations may include three (3) or more resonators.For example, a single source resonator may transfer energy to multipledevice resonators or multiple devices. Energy may be transferred from afirst device to a second, and then from the second device to the third,and so forth. Multiple sources may transfer energy to a single device orto multiple devices connected to a single device resonator or tomultiple devices connected to multiple device resonators. Resonators mayserve alternately or simultaneously as sources, devices, and/or they maybe used to relay power from a source in one location to a device inanother location. Intermediate electromagnetic resonators may be used toextend the distance range of wireless energy transfer systems and/or togenerate areas of concentrated magnetic near-fields. Multiple resonatorsmay be daisy-chained together, exchanging energy over extended distancesand with a wide range of sources and devices. For example, a sourceresonator may transfer power to a device resonator via several repeaterresonators. Energy from a source may be transferred to a first repeaterresonator, the first repeater resonator may transfer the power to asecond repeater resonator and the second to a third and so on until thefinal repeater resonator transfers its energy to a device resonator. Inthis respect the range or distance of wireless energy transfer may beextended and/or tailored by adding repeater resonators. High powerlevels may be split between multiple sources, transferred to multipledevices and recombined at a distant location.

The resonators may be designed using coupled mode theory models, circuitmodels, electromagnetic field models, and the like. The resonators maybe designed to have tunable characteristic sizes. The resonators may bedesigned to handle different power levels. In exemplary embodiments,high power resonators may require larger conductors and higher currentor voltage rated components than lower power resonators.

FIG. 1 shows a diagram of exemplary configurations and arrangements of awireless energy transfer system. A wireless energy transfer system mayinclude at least one source resonator (R1)104 (optionally R6, 112)coupled to an energy source 102 and optionally a sensor and control unit108. The energy source may be a source of any type of energy capable ofbeing converted into electrical energy that may be used to drive thesource resonator 104. The energy source may be a battery, a solar panel,the electrical mains, a wind or water turbine, an electromagneticresonator, a generator, and the like. The electrical energy used todrive the magnetic resonator is converted into oscillating magneticfields by the resonator. The oscillating magnetic fields may be capturedby other resonators which may be device resonators (R2) 106, (R3) 116that are optionally coupled to an energy drain 110. The oscillatingfields may be optionally coupled to repeater resonators (R4, R5) thatare configured to extend or tailor the wireless energy transfer region.Device resonators may capture the magnetic fields in the vicinity ofsource resonator(s), repeater resonators and other device resonators andconvert them into electrical energy that may be used by an energy drain.The energy drain 110 may be an electrical, electronic, mechanical orchemical device and the like configured to receive electrical energy.Repeater resonators may capture magnetic fields in the vicinity ofsource, device and repeater resonator(s) and may pass the energy on toother resonators.

A wireless energy transfer system may comprise a single source resonator104 coupled to an energy source 102 and a single device resonator 106coupled to an energy drain 110. In embodiments a wireless energytransfer system may comprise multiple source resonators coupled to oneor more energy sources and may comprise multiple device resonatorscoupled to one or more energy drains.

In embodiments the energy may be transferred directly between a sourceresonator 104 and a device resonator 106. In other embodiments theenergy may be transferred from one or more source resonators 104, 112 toone or more device resonators 106, 116 via any number of intermediateresonators which may be device resonators, source resonators, repeaterresonators, and the like. Energy may be transferred via a network orarrangement of resonators 114 that may include subnetworks 118, 120arranged in any combination of topologies such as token ring, mesh, adhoc, and the like.

In embodiments the wireless energy transfer system may comprise acentralized sensing and control system 108. In embodiments parameters ofthe resonators, energy sources, energy drains, network topologies,operating parameters, etc. may be monitored and adjusted from a controlprocessor to meet specific operating parameters of the system. A centralcontrol processor may adjust parameters of individual components of thesystem to optimize global energy transfer efficiency, to optimize theamount of power transferred, and the like. Other embodiments may bedesigned to have a substantially distributed sensing and control system.Sensing and control may be incorporated into each resonator or group ofresonators, energy sources, energy drains, and the like and may beconfigured to adjust the parameters of the individual components in thegroup to maximize the power delivered, to maximize energy transferefficiency in that group and the like.

In embodiments, components of the wireless energy transfer system mayhave wireless or wired data communication links to other components suchas devices, sources, repeaters, power sources, resonators, and the likeand may transmit or receive data that can be used to enable thedistributed or centralized sensing and control. A wireless communicationchannel may be separate from the wireless energy transfer channel, or itmay be the same. In one embodiment the resonators used for powerexchange may also be used to exchange information. In some cases,information may be exchanged by modulating a component in a source ordevice circuit and sensing that change with port parameter or othermonitoring equipment. Resonators may signal each other by tuning,changing, varying, dithering, and the like, the resonator parameterssuch as the impedance of the resonators which may affect the reflectedimpedance of other resonators in the system. The systems and methodsdescribed herein may enable the simultaneous transmission of power andcommunication signals between resonators in wireless power transmissionsystems, or it may enable the transmission of power and communicationsignals during different time periods or at different frequencies usingthe same magnetic fields that are used during the wireless energytransfer. In other embodiments wireless communication may be enabledwith a separate wireless communication channel such as WiFi, Bluetooth,Infrared, and the like.

In embodiments, a wireless energy transfer system may include multipleresonators and overall system performance may be improved by control ofvarious elements in the system. For example, devices with lower powerrequirements may tune their resonant frequency away from the resonantfrequency of a high-power source that supplies power to devices withhigher power requirements. In this way, low and high power devices maysafely operate or charge from a single high power source. In addition,multiple devices in a charging zone may find the power available to themregulated according to any of a variety of consumption controlalgorithms such as First-Come-First-Serve, Best Effort, GuaranteedPower, etc. The power consumption algorithms may be hierarchical innature, giving priority to certain users or types of devices, or it maysupport any number of users by equally sharing the power that isavailable in the source. Power may be shared by any of the multiplexingtechniques described in this disclosure.

In embodiments electromagnetic resonators may be realized or implementedusing a combination of shapes, structures, and configurations.Electromagnetic resonators may include an inductive element, adistributed inductance, or a combination of inductances with a totalinductance, L, and a capacitive element, a distributed capacitance, or acombination of capacitances, with a total capacitance, C. A minimalcircuit model of an electromagnetic resonator comprising capacitance,inductance and resistance, is shown in FIG. 2F. The resonator mayinclude an inductive element 238 and a capacitive element 240. Providedwith initial energy, such as electric field energy stored in thecapacitor 240, the system will oscillate as the capacitor dischargestransferring energy into magnetic field energy stored in the inductor238 which in turn transfers energy back into electric field energystored in the capacitor 240. Intrinsic losses in these electromagneticresonators include losses due to resistance in the inductive andcapacitive elements and to radiation losses, and are represented by theresistor, R, 242 in FIG. 2F.

FIG. 2A shows a simplified drawing of an exemplary magnetic resonatorstructure. The magnetic resonator may include a loop of conductor actingas an inductive element 202 and a capacitive element 204 at the ends ofthe conductor loop. The inductor 202 and capacitor 204 of anelectromagnetic resonator may be bulk circuit elements, or theinductance and capacitance may be distributed and may result from theway the conductors are formed, shaped, or positioned, in the structure.

For example, the inductor 202 may be realized by shaping a conductor toenclose a surface area, as shown in FIG. 2A. This type of resonator maybe referred to as a capacitively-loaded loop inductor. Note that we mayuse the terms “loop” or “coil” to indicate generally a conductingstructure (wire, tube, strip, etc.), enclosing a surface of any shapeand dimension, with any number of turns. In FIG. 2A, the enclosedsurface area is circular, but the surface may be any of a wide varietyof other shapes and sizes and may be designed to achieve certain systemperformance specifications. In embodiments the inductance may berealized using inductor elements, distributed inductance, networks,arrays, series and parallel combinations of inductors and inductances,and the like. The inductance may be fixed or variable and may be used tovary impedance matching as well as resonant frequency operatingconditions.

There are a variety of ways to realize the capacitance required toachieve the desired resonant frequency for a resonator structure.Capacitor plates 204 may be formed and utilized as shown in FIG. 2A, orthe capacitance may be distributed and be realized between adjacentwindings of a multi-loop conductor. The capacitance may be realizedusing capacitor elements, distributed capacitance, networks, arrays,series and parallel combinations of capacitances, and the like. Thecapacitance may be fixed or variable and may be used to vary impedancematching as well as resonant frequency operating conditions.

The inductive elements used in magnetic resonators may contain more thanone loop and may spiral inward or outward or up or down or in somecombination of directions. In general, the magnetic resonators may havea variety of shapes, sizes and number of turns and they may be composedof a variety of conducing materials. The conductor 210, for example, maybe a wire, a Litz wire, a ribbon, a pipe, a trace formed from conductingink, paint, gels, and the like or from single or multiple traces printedon a circuit board. An exemplary embodiment of a trace pattern on asubstrate 208 forming inductive loops is depicted in FIG. 2B.

In embodiments the inductive elements may be formed using magneticmaterials of any size, shape thickness, and the like, and of materialswith a wide range of permeability and loss values. These magneticmaterials may be solid blocks, they may enclose hollow volumes, they maybe formed from many smaller pieces of magnetic material tiled and orstacked together, and they may be integrated with conducting sheets orenclosures made from highly conducting materials. Conductors may bewrapped around the magnetic materials to generate the magnetic field.These conductors may be wrapped around one or more than one axis of thestructure. Multiple conductors may be wrapped around the magneticmaterials and combined in parallel, or in series, or via a switch toform customized near-field patterns and/or to orient the dipole momentof the structure. Examples of resonators comprising magnetic materialare depicted in FIGS. 2C, 2D, 2E. In FIG. 2D the resonator comprisesloops of conductor 224 wrapped around a core of magnetic material 222creating a structure that has a magnetic dipole moment 228 that isparallel to the axis of the loops of the conductor 224. The resonatormay comprise multiple loops of conductor 216, 212 wrapped in orthogonaldirections around the magnetic material 214 forming a resonator with amagnetic dipole moment 218, 220 that may be oriented in more than onedirection as depicted in FIG. 2C, depending on how the conductors aredriven.

An electromagnetic resonator may have a characteristic, natural, orresonant frequency determined by its physical properties. This resonantfrequency is the frequency at which the energy stored by the resonatoroscillates between that stored by the electric field, W_(E),(W_(E)=q²/2C, where q is the charge on the capacitor, C) and that storedby the magnetic field, W_(B), (W_(B)=Li²/2, where i is the currentthrough the inductor, L) of the resonator. The frequency at which thisenergy is exchanged may be called the characteristic frequency, thenatural frequency, or the resonant frequency of the resonator, and isgiven by ω,

$\omega = {{2\pi \; f} = {\sqrt{\frac{1}{LC}}.}}$

The resonant frequency of the resonator may be changed by tuning theinductance, L, and/or the capacitance, C, of the resonator. In oneembodiment system parameters are dynamically adjustable or tunable toachieve as close as possible to optimal operating conditions. However,based on the discussion above, efficient enough energy exchange may berealized even if some system parameters are not variable or componentsare not capable of dynamic adjustment.

In embodiments a resonator may comprise an inductive element coupled tomore than one capacitor arranged in a network of capacitors and circuitelements. In embodiments the coupled network of capacitors and circuitelements may be used to define more than one resonant frequency of theresonator. In embodiments a resonator may be resonant, or partiallyresonant, at more than one frequency.

In embodiments, a wireless power source may comprise of at least oneresonator coil coupled to a power supply, which may be a switchingamplifier, such as a class-D amplifier or a class-E amplifier or acombination thereof. In this case, the resonator coil is effectively apower load to the power supply. In embodiments, a wireless power devicemay comprise of at least one resonator coil coupled to a power load,which may be a switching rectifier, such as a class-D rectifier or aclass-E rectifier or a combination thereof. In this case, the resonatorcoil is effectively a power supply for the power load, and the impedanceof the load directly relates also to the work-drainage rate of the loadfrom the resonator coil. The efficiency of power transmission between apower supply and a power load may be impacted by how closely matched theoutput impedance of the power source is to the input impedance of theload. Power may be delivered to the load at a maximum possibleefficiency, when the input impedance of the load is equal to the complexconjugate of the internal impedance of the power supply. Designing thepower supply or power load impedance to obtain a maximum powertransmission efficiency is often called “impedance matching”, and mayalso referred to as optimizing the ratio of useful-to-lost powers in thesystem. Impedance matching may be performed by adding networks or setsof elements such as capacitors, inductors, transformers, switches,resistors, and the like, to form impedance matching networks between apower supply and a power load. In embodiments, mechanical adjustmentsand changes in element positioning may be used to achieve impedancematching. For varying loads, the impedance matching network may includevariable components that are dynamically adjusted to ensure that theimpedance at the power supply terminals looking towards the load and thecharacteristic impedance of the power supply remain substantiallycomplex conjugates of each other, even in dynamic environments andoperating scenarios.

In embodiments, impedance matching may be accomplished by tuning theduty cycle, and/or the phase, and/or the frequency of the driving signalof the power supply or by tuning a physical component within the powersupply, such as a capacitor. Such a tuning mechanism may be advantageousbecause it may allow impedance matching between a power supply and aload without the use of a tunable impedance matching network, or with asimplified tunable impedance matching network, such as one that hasfewer tunable components for example. In embodiments, tuning the dutycycle, and/or frequency, and/or phase of the driving signal to a powersupply may yield a dynamic impedance matching system with an extendedtuning range or precision, with higher power, voltage and/or currentcapabilities, with faster electronic control, with fewer externalcomponents, and the like.

In some wireless energy transfer systems the parameters of the resonatorsuch as the inductance may be affected by environmental conditions suchas surrounding objects, temperature, orientation, number and position ofother resonators and the like. Changes in operating parameters of theresonators may change certain system parameters, such as the efficiencyof transferred power in the wireless energy transfer. For example,high-conductivity materials located near a resonator may shift theresonant frequency of a resonator and detune it from other resonantobjects. In some embodiments, a resonator feedback mechanism is employedthat corrects its frequency by changing a reactive element (e.g., aninductive element or capacitive element). In order to achieve acceptablematching conditions, at least some of the system parameters may need tobe dynamically adjustable or tunable. All the system parameters may bedynamically adjustable or tunable to achieve approximately the optimaloperating conditions. However, efficient enough energy exchange may berealized even if all or some system parameters are not variable. In someexamples, at least some of the devices may not be dynamically adjusted.In some examples, at least some of the sources may not be dynamicallyadjusted. In some examples, at least some of the intermediate resonatorsmay not be dynamically adjusted. In some examples, none of the systemparameters may be dynamically adjusted.

In some embodiments changes in parameters of components may be mitigatedby selecting components with characteristics that change in acomplimentary or opposite way or direction when subjected to differencesin operating environment or operating point. In embodiments, a systemmay be designed with components, such as capacitors, that have anopposite dependence or parameter fluctuation due to temperature, powerlevels, frequency, and the like. In some embodiments, the componentvalues as a function of temperature may be stored in a look-up table ina system microcontroller and the reading from a temperature sensor maybe used in the system control feedback loop to adjust other parametersto compensate for the temperature induced component value changes.

In some embodiments the changes in parameter values of components may becompensated with active tuning circuits comprising tunable components.Circuits that monitor the operating environment and operating point ofcomponents and system may be integrated in the design. The monitoringcircuits may provide the signals necessary to actively compensate forchanges in parameters of components. For example, a temperature readingmay be used to calculate expected changes in, or to indicate previouslymeasured values of, capacitance of the system allowing compensation byswitching in other capacitors or tuning capacitors to maintain thedesired capacitance over a range of temperatures. In embodiments, the RFamplifier switching waveforms may be adjusted to compensate forcomponent value or load changes in the system. In some embodiments thechanges in parameters of components may be compensated with activecooling, heating, active environment conditioning, and the like.

The parameter measurement circuitry may measure or monitor certainpower, voltage, and current, signals in the system, and processors orcontrol circuits may adjust certain settings or operating parametersbased on those measurements. In addition the magnitude and phase ofvoltage and current signals, and the magnitude of the power signals,throughout the system may be accessed to measure or monitor the systemperformance. The measured signals referred to throughout this disclosuremay be any combination of port parameter signals, as well as voltagesignals, current signals, power signals, temperatures signals and thelike. These parameters may be measured using analog or digitaltechniques, they may be sampled and processed, and they may be digitizedor converted using a number of known analog and digital processingtechniques. In embodiments, preset values of certain measured quantitiesare loaded in a system controller or memory location and used in variousfeedback and control loops. In embodiments, any combination of measured,monitored, and/or preset signals may be used in feedback circuits orsystems to control the operation of the resonators and/or the system.

Adjustment algorithms may be used to adjust the frequency, Q, and/orimpedance of the magnetic resonators. The algorithms may take as inputsreference signals related to the degree of deviation from a desiredoperating point for the system and may output correction or controlsignals related to that deviation that control variable or tunableelements of the system to bring the system back towards the desiredoperating point or points. The reference signals for the magneticresonators may be acquired while the resonators are exchanging power ina wireless power transmission system, or they may be switched out of thecircuit during system operation. Corrections to the system may beapplied or performed continuously, periodically, upon a thresholdcrossing, digitally, using analog methods, and the like.

In embodiments, lossy extraneous materials and objects may introducepotential reductions in efficiencies by absorbing the magnetic and/orelectric energy of the resonators of the wireless power transmissionsystem. Those impacts may be mitigated in various embodiments bypositioning resonators to minimize the effects of the lossy extraneousmaterials and objects and by placing structural field shaping elements(e.g., conductive structures, plates and sheets, magnetic materialstructures, plates and sheets, and combinations thereof) to minimizetheir effect.

One way to reduce the impact of lossy materials on a resonator is to usehigh-conductivity materials, magnetic materials, or combinations thereofto shape the resonator fields such that they avoid the lossy objects. Inan exemplary embodiment, a layered structure of high-conductivitymaterial and magnetic material may tailor, shape, direct, reorient, etc.the resonator's electromagnetic fields so that they avoid lossy objectsin their vicinity by deflecting the fields. FIG. 2D shows a top view ofa resonator with a sheet of conductor 226 below the magnetic materialthat may used to tailor the fields of the resonator so that they avoidlossy objects that may be below the sheet of conductor 226. The layer orsheet of good 226 conductor may comprise any high conductivity materialssuch as copper, silver, aluminum, as may be most appropriate for a givenapplication. In certain embodiments, the layer or sheet of goodconductor is thicker than the skin depth of the conductor at theresonator operating frequency. The conductor sheet may be preferablylarger than the size of the resonator, extending beyond the physicalextent of the resonator.

In environments and systems where the amount of power being transmittedcould present a safety hazard to a person or animal that may intrudeinto the active field volume, safety measures may be included in thesystem. In embodiments where power levels require particularized safetymeasures, the packaging, structure, materials, and the like of theresonators may be designed to provide a spacing or “keep away” zone fromthe conducting loops in the magnetic resonator. To provide furtherprotection, high-Q resonators and power and control circuitry may belocated in enclosures that confine high voltages or currents to withinthe enclosure, that protect the resonators and electrical componentsfrom weather, moisture, sand, dust, and other external elements, as wellas from impacts, vibrations, scrapes, explosions, and other types ofmechanical shock. Such enclosures call for attention to various factorssuch as thermal dissipation to maintain an acceptable operatingtemperature range for the electrical components and the resonator. Inembodiments, enclosure may be constructed of non-lossy materials such ascomposites, plastics, wood, concrete, and the like and may be used toprovide a minimum distance from lossy objects to the resonatorcomponents. A minimum separation distance from lossy objects orenvironments which may include metal objects, salt water, oil and thelike, may improve the efficiency of wireless energy transfer. Inembodiments, a “keep away” zone may be used to increase the perturbed Qof a resonator or system of resonators. In embodiments a minimumseparation distance may provide for a more reliable or more constantoperating parameters of the resonators.

In embodiments, resonators and their respective sensor and controlcircuitry may have various levels of integration with other electronicand control systems and subsystems. In some embodiments the power andcontrol circuitry and the device resonators are completely separatemodules or enclosures with minimal integration to existing systems,providing a power output and a control and diagnostics interface. Insome embodiments a device is configured to house a resonator and circuitassembly in a cavity inside the enclosure, or integrated into thehousing or enclosure of the device.

Example Resonator Circuitry

FIGS. 3 and 4 show high level block diagrams depicting power generation,monitoring, and control components for exemplary sources of a wirelessenergy transfer system. FIG. 3 is a block diagram of a source comprisinga half-bridge switching power amplifier and some of the associatedmeasurement, tuning, and control circuitry. FIG. 4 is a block diagram ofa source comprising a full-bridge switching amplifier and some of theassociated measurement, tuning, and control circuitry.

The half bridge system topology depicted in FIG. 3 may comprise aprocessing unit that executes a control algorithm 328. The processingunit executing a control algorithm 328 may be a microcontroller, anapplication specific circuit, a field programmable gate array, aprocessor, a digital signal processor, and the like. The processing unitmay be a single device or it may be a network of devices. The controlalgorithm may run on any portion of the processing unit. The algorithmmay be customized for certain applications and may comprise acombination of analog and digital circuits and signals. The masteralgorithm may measure and adjust voltage signals and levels, currentsignals and levels, signal phases, digital count settings, and the like.

The system may comprise an optional source/device and/or source/otherresonator communication controller 332 coupled to wireless communicationcircuitry 312. The optional source/device and/or source/other resonatorcommunication controller 332 may be part of the same processing unitthat executes the master control algorithm, it may a part or a circuitwithin a microcontroller 302, it may be external to the wireless powertransmission modules, it may be substantially similar to communicationcontrollers used in wire powered or battery powered applications butadapted to include some new or different functionality to enhance orsupport wireless power transmission.

The system may comprise a PWM generator 306 coupled to at least twotransistor gate drivers 334 and may be controlled by the controlalgorithm. The two transistor gate drivers 334 may be coupled directlyor via gate drive transformers to two power transistors 336 that drivethe source resonator coil 344 through impedance matching networkcomponents 342. The power transistors 336 may be coupled and poweredwith an adjustable DC supply 304 and the adjustable DC supply 304 may becontrolled by a variable bus voltage, Vbus. The Vbus controller may becontrolled by the control algorithm 328 and may be part of, orintegrated into, a microcontroller 302 or other integrated circuits. TheVbus controller 326 may control the voltage output of an adjustable DCsupply 304 which may be used to control power output of the amplifierand power delivered to the resonator coil 344. In other embodiments, thePWM generator 306 may control the phase angle between the currentwaveform through the load and the switching times of the powertransistors 336 which may be used to control power output from theamplifier and power delivered to the resonator coil 344. In otherembodiments, the PWM generator 306 may control the duty cycle of theswitch closure time to control power output from that amplifier andpower delivered to the resonator coil 344.

The system may comprise sensing and measurement circuitry includingsignal filtering and buffering circuits 318, 320 that may shape, modify,filter, process, buffer, and the like, signals prior to their input toprocessors and/or converters such as analog to digital converters (ADC)314, 316, for example. The processors and converters such as ADCs 314,316 may be integrated into a microcontroller 302 or may be separatecircuits that may be coupled to a processing core 330. Based on measuredsignals, the control algorithm 328 may generate, limit, initiate,extinguish, control, adjust, or modify the operation of any of the PWMgenerator 306, the communication controller 332, the Vbus control 326,the source impedance matching controller 338, the filter/bufferingelements, 318, 320, the converters, 314, 316, the resonator coil 344,and may be part of, or integrated into, a microcontroller 302 or aseparate circuit. The impedance matching networks 342 and resonatorcoils 344 may include electrically controllable, variable, or tunablecomponents such as capacitors, switches, inductors, and the like, asdescribed herein, and these components may have their component valuesor operating points adjusted according to signals received from thesource impedance matching controller 338. Components may be tuned toadjust the operation and characteristics of the resonator including thepower delivered to and by the resonator, the resonant frequency of theresonator, the impedance of the resonator, the Q of the resonator, andany other coupled systems, and the like. The resonator may be any typeor structure resonator described herein including a capacitively loadedloop resonator, a planer resonator comprising a magnetic material or anycombination thereof.

The full bridge system topology depicted in FIG. 4 may comprise aprocessing unit that executes a master control algorithm 328. Theprocessing unit executing the control algorithm 328 may be amicrocontroller, an application specific circuit, a field programmablegate array, a processor, a digital signal processor, and the like. Thesystem may comprise a source/device and/or source/other resonatorcommunication controller 332 coupled to wireless communication circuitry312. The source/device and/or source/other resonator communicationcontroller 332 may be part of the same processing unit that executesthat master control algorithm, it may a part or a circuit within amicrocontroller 302, it may be external to the wireless powertransmission modules, it may be substantially similar to communicationcontrollers used in wire powered or battery powered applications butadapted to include some new or different functionality to enhance orsupport wireless power transmission.

The system may comprise a PWM generator 410 with at least two outputscoupled to at least four transistor gate drivers 334 that may becontrolled by signals generated in a master control algorithm. The fourtransistor gate drivers 334 may be coupled to four power transistors 336directly or via gate drive transformers that may drive the sourceresonator coil 344 through impedance matching networks 342. The powertransistors 336 may be coupled and powered with an adjustable DC supply304 and the adjustable DC supply 304 may be controlled by a Vbuscontroller 326 which may be controlled by a master control algorithm.The Vbus controller 326 may control the voltage output of the adjustableDC supply 304 which may be used to control power output of the amplifierand power delivered to the resonator coil 344. In other embodiments, thePWM generator 410 may control the relative phase angle for the twohalves of the bridge between the current waveform through the load andthe switching times of the power transistors 336 which may be used tocontrol power output from the amplifier and power delivered to theresonator coil 344. In other embodiments, the PWM generator 410 maycontrol the duty cycle of the switch closure time to control poweroutput from that amplifier and power delivered to the resonator coil344.

The system may comprise sensing and measurement circuitry includingsignal filtering and buffering circuits 318, 320 and differential/singleended conversion circuitry 402, 404 that may shape, modify, filter,process, buffer, and the like, signals prior to being input toprocessors and/or converters such as analog to digital converters (ADC)314, 316. The processors and/or converters such as ADC 314, 316 may beintegrated into a microcontroller 302 or may be separate circuits thatmay be coupled to a processing core 330. Based on measured signals, themaster control algorithm may generate, limit, initiate, extinguish,control, adjust, or modify the operation of any of the PWM generator410, the communication controller 332, the Vbus controller 326, thesource impedance matching controller 338, the filter/buffering elements,318, 320, differential/single ended conversion circuitry 402, 404, theconverters, 314, 316, the resonator coil 344, and may be part of orintegrated into a microcontroller 302 or a separate circuit.

Impedance matching networks 342 and resonator coils 344 may compriseelectrically controllable, variable, or tunable components such ascapacitors, switches, inductors, and the like, as described herein, andthese components may have their component values or operating pointsadjusted according to signals received from the source impedancematching controller 338. Components may be tuned to enable tuning of theoperation and characteristics of the resonator including the powerdelivered to and by the resonator, the resonant frequency of theresonator, the impedance of the resonator, the Q of the resonator, andany other coupled systems, and the like. The resonator may be any typeor structure resonator described herein including a capacitively loadedloop resonator, a planar resonator comprising a magnetic material or anycombination thereof.

Impedance matching networks may comprise fixed value components such ascapacitors, inductors, and networks of components as described herein.Parts of the impedance matching networks, A, B and C, may compriseinductors, capacitors, transformers, and series and parallelcombinations of such components, as described herein. In someembodiments, parts of the impedance matching networks A, B, and C, maybe empty (short-circuited). In some embodiments, part B comprises aseries combination of an inductor and a capacitor, and part C is empty.

The full bridge topology may allow operation at higher output powerlevels using the same DC bus voltage as an equivalent half bridgeamplifier. The half bridge exemplary topology of FIG. 3 may provide asingle-ended drive signal, while the exemplary full bridge topology ofFIG. 4 may provide a differential drive to the source resonator 308. Theimpedance matching topologies and components and the resonator structuremay be different for the two systems, as discussed herein.

The exemplary systems depicted in FIGS. 3 and 4 may further includefault detection circuitry 340 that may be used to trigger the shutdownof the microcontroller in the source amplifier or to change or interruptthe operation of the amplifier. This protection circuitry may comprise ahigh speed comparator or comparators to monitor the amplifier returncurrent, the amplifier bus voltage (Vbus) from the DC supply 304, thevoltage across the source resonator 308 and/or the optional tuningboard, or any other voltage or current signals that may cause damage tocomponents in the system or may yield undesirable operating conditions.Preferred embodiments may depend on the potentially undesirableoperating modes associated with different applications. In someembodiments, protection circuitry may not be implemented or circuits maynot be populated. In some embodiments, system and component protectionmay be implemented as part of a master control algorithm and othersystem monitoring and control circuits. In embodiments, dedicated faultcircuitry 340 may include an output (not shown) coupled to a mastercontrol algorithm 328 that may trigger a system shutdown, a reduction ofthe output power (e.g. reduction of Vbus), a change to the PWMgenerator, a change in the operating frequency, a change to a tuningelement, or any other reasonable action that may be implemented by thecontrol algorithm 328 to adjust the operating point mode, improve systemperformance, and/or provide protection.

The exemplary systems depicted in FIGS. 3 and 4 may be configured sothat the DC (or slowly varying AC) power supplied to the switches can befrom a power source with varying power and/or output impedance. Forexample, the DC supply 304 may comprise a battery with an output voltageand output resistance that both vary as a function of the battery chargestate. Or, the DC supply 304 may comprise a photovoltaic panel with avoltage and/or current that may vary as a function of environmentalconditions such as solar illumination and temperature. In embodiments,the Vbus controller 326 may allow for tuning of the output impedance ofthe variable power source so that efficient wireless energy transfer ispossible. In other embodiments, the PWM generator may allow foradjustment of the phase angle for switching the transistors 336 so thatthe optimum power can be extracted from the variable power source. Forexample, the switching times may be selected so that the input impedanceof the amplifier matches the output impedance of the variable powersource. In other examples, such as for the photovoltaic panel, theswitching times may be selected so that an impedance is applied to theoutput of the photovoltaic panel that maximizes energy extraction fromthe photovoltaic panel. Those skilled in the art will understand thatthis general principle applies to other variable power sources includingwind-powered generators, heat-powered generators, water-poweredgenerators, fuel cells, batteries, and the like.

As described herein, sources in wireless power transfer systems may usea measurement of the input impedance of the impedance matching network342 driving source resonator coil 344 as an error or control signal fora system control loop that may be part of the master control algorithm.In exemplary embodiments, variations in any combination of threeparameters may be used to tune the wireless power source to compensatefor changes in environmental conditions, for changes in coupling, forchanges in device power demand, for changes in module, circuit,component or subsystem performance, for an increase or decrease in thenumber or sources, devices, or repeaters in the system, for userinitiated changes, and the like. In exemplary embodiments, changes tothe amplifier duty cycle, to the component values of the variableelectrical components such as variable capacitors and inductors, and tothe DC bus voltage may be used to change the operating point oroperating range of the wireless source and improve some system operatingvalue. The specifics of the control algorithms employed for differentapplications may vary depending on the desired system performance andbehavior.

Impedance measurement circuitry such as described herein, and shown inFIGS. 3 and 4, may be implemented using two-channel simultaneoussampling ADCs and these ADCs may be integrated into a microcontrollerchip or may be part of a separate circuit. Simultaneously sampling ofthe voltage and current signals at the input to a source resonator'simpedance matching network and/or at the source resonator, may yield thephase and magnitude information of the current and voltage signals andmay be processed using known signal processing techniques to yieldcomplex impedance parameters. In some embodiments, monitoring only thevoltage signals or only the current signals may be sufficient.

The impedance measurements described herein may use direct samplingmethods which may be relatively simpler than some other known samplingmethods. In embodiments, measured voltage and current signals may beconditioned, filtered and scaled by filtering/buffering circuitry beforebeing input to ADCs. In embodiments, the filter/buffering circuitry maybe adjustable to work at a variety of signal levels and frequencies, andcircuit parameters such as filter shapes and widths may be adjustedmanually, electronically, automatically, in response to a controlsignal, by the master control algorithm, and the like. Exemplaryembodiments of filter/buffering circuits are shown in FIGS. 3, 4, and 5.

FIG. 5 shows more detailed views of exemplary circuit components thatmay be used in filter/buffering circuitry. In embodiments, and dependingon the types of ADCs used in the system designs, single-ended amplifiertopologies may reduce the complexity of the analog signal measurementpaths used to characterize system, subsystem, module and/or componentperformance by eliminating the need for hardware to convert fromdifferential to single-ended signal formats. In other implementations,differential signal formats may be preferable. The implementations shownin FIG. 5 are exemplary, and should not be construed to be the onlypossible way to implement the functionality described herein. Rather itshould be understood that the analog signal path may employ componentswith different input requirements and hence may have different signalpath architectures.

In both the single ended and differential amplifier topologies, theinput current to the impedance matching networks 342 driving theresonator coils 344 may be obtained by measuring the voltage across acapacitor 324, or via a current sensor of some type. For the exemplarysingle-ended amplifier topology in FIG. 3, the current may be sensed onthe ground return path from the impedance matching network 342. For theexemplary differential power amplifier depicted in FIG. 4, the inputcurrent to the impedance matching networks 342 driving the resonatorcoils 344 may be measured using a differential amplifier across theterminals of a capacitor 324 or via a current sensor of some type. Inthe differential topology of FIG. 4, the capacitor 324 may be duplicatedat the negative output terminal of the source power amplifier.

In both topologies, after single ended signals representing the inputvoltage and current to the source resonator and impedance matchingnetwork are obtained, the signals may be filtered 502 to obtain thedesired portions of the signal waveforms. In embodiments, the signalsmay be filtered to obtain the fundamental component of the signals. Inembodiments, the type of filtering performed, such as low pass,bandpass, notch, and the like, as well as the filter topology used, suchas elliptical, Chebyshev, Butterworth, and the like, may depend on thespecific requirements of the system. In some embodiments, no filteringwill be required.

The voltage and current signals may be amplified by an optionalamplifier 504. The gain of the optional amplifier 504 may be fixed orvariable. The gain of the amplifier may be controlled manually,electronically, automatically, in response to a control signal, and thelike. The gain of the amplifier may be adjusted in a feedback loop, inresponse to a control algorithm, by the master control algorithm, andthe like. In embodiments, required performance specifications for theamplifier may depend on signal strength and desired measurementaccuracy, and may be different for different application scenarios andcontrol algorithms.

The measured analog signals may have a DC offset added to them, 506,which may be required to bring the signals into the input voltage rangeof the ADC which for some systems may be 0 to 3.3V. In some systems thisstage may not be required, depending on the specifications of theparticular ADC used.

As described above, the efficiency of power transmission between a powergenerator and a power load may be impacted by how closely matched theoutput impedance of the generator is to the input impedance of the load.In an exemplary system as shown in FIG. 6A, power may be delivered tothe load at a maximum possible efficiency, when the input impedance ofthe load 604 is equal to the complex conjugate of the internal impedanceof the power generator or the power amplifier 602. Designing thegenerator or load impedance to obtain a high and/or maximum powertransmission efficiency may be called “impedance matching”. Impedancematching may be performed by inserting appropriate networks or sets ofelements such as capacitors, resistors, inductors, transformers,switches and the like, to form an impedance matching network 606,between a power generator 602 and a power load 604 as shown in FIG. 6B.In other embodiments, mechanical adjustments and changes in elementpositioning may be used to achieve impedance matching. As describedabove for varying loads, the impedance matching network 606 may includevariable components that are dynamically adjusted to ensure that theimpedance at the generator terminals looking towards the load and thecharacteristic impedance of the generator remain substantially complexconjugates of each other, even in dynamic environments and operatingscenarios. In embodiments, dynamic impedance matching may beaccomplished by tuning the duty cycle, and/or the phase, and/or thefrequency of the driving signal of the power generator or by tuning aphysical component within the power generator, such as a capacitor, asdepicted in FIG. 6C. Such a tuning mechanism may be advantageous becauseit may allow impedance matching between a power generator 608 and a loadwithout the use of a tunable impedance matching network, or with asimplified tunable impedance matching network 606, such as one that hasfewer tunable components for example. In embodiments, tuning the dutycycle, and/or frequency, and/or phase of the driving signal to a powergenerator may yield a dynamic impedance matching system with an extendedtuning range or precision, with higher power, voltage and/or currentcapabilities, with faster electronic control, with fewer externalcomponents, and the like. The impedance matching methods, architectures,algorithms, protocols, circuits, measurements, controls, and the like,described below, may be useful in systems where power generators drivehigh-Q magnetic resonators and in high-Q wireless power transmissionsystems as described herein. In wireless power transfer systems a powergenerator may be a power amplifier driving a resonator, sometimesreferred to as a source resonator, which may be a load to the poweramplifier. In wireless power applications, it may be preferable tocontrol the impedance matching between a power amplifier and a resonatorload to control the efficiency of the power delivery from the poweramplifier to the resonator. The impedance matching may be accomplished,or accomplished in part, by tuning or adjusting the duty cycle, and/orthe phase, and/or the frequency of the driving signal of the poweramplifier that drives the resonator.

Efficiency of Switching Amplifiers

Switching amplifiers, such as class D, E, F amplifiers, and the like orany combinations thereof, deliver power to a load at a maximumefficiency when almost no power is dissipated in the switching elementsof the amplifier. This operating condition may be accomplished bydesigning the system so that the switching operations which are mostcritical (namely those that are most likely to lead to switching losses)are done when both the voltage across the switching element and thecurrent through the switching element are nearly zero. These conditionsmay be referred to as Zero Voltage Switching (ZVS) and Zero CurrentSwitching (ZCS) conditions respectively. When an amplifier operates atZVS and ZCS either the voltage across the switching element or thecurrent through the switching element is zero and thus no power can bedissipated in the switch. Since a switching amplifier may convert DC (orvery low frequency AC) power to AC power at a specific frequency orrange of frequencies, a filter may be introduced before the load toprevent unwanted harmonics that may be generated by the switchingprocess from reaching the load and being dissipated there. Inembodiments, a switching amplifier may be designed to operate at maximumefficiency of power conversion, when connected to a resonant load, witha quality factor (say Q>5), and of a specific impedanceZ_(o)*=R_(o)+jX_(o), which leads to simultaneous ZVS and ZCS. We defineZ_(o)=R_(o)−jX, as the characteristic impedance of the amplifier, sothat achieving maximum power transmission efficiency is equivalent toimpedance matching the resonant load to the characteristic impedance ofthe amplifier.

In a switching amplifier, the switching frequency of the switchingelements, f_(switch), wherein f_(switch)=ω/2π and the duty cycle, dc, ofthe ON switch-state duration of the switching elements may be the samefor all switching elements of the amplifier. In this specification, wewill use the term “class D” to denote both class D and class DEamplifiers, that is, switching amplifiers with dc<=50%.

The value of the characteristic impedance of the amplifier may depend onthe operating frequency, the amplifier topology, and the switchingsequence of the switching elements. In some embodiments, the switchingamplifier may be a half-bridge topology and, in some embodiments, afull-bridge topology. In some embodiments, the switching amplifier maybe class D and, in some embodiments, class E. In any of the aboveembodiments, assuming the elements of the bridge are symmetric, thecharacteristic impedance of the switching amplifier has the form

R _(o) =F _(R)(dc)/ωC _(a) ,X _(o) =F _(X)(dc)/ωC _(a),  (1)

where dc is the duty cycle of ON switch-state of the switching elements,the functions F_(R) (dc) and F_(X)(dc) are plotted in FIG. 7 (both forclass D and E), ω is the frequency at which the switching elements areswitched, and C_(a)=n_(a)C_(switch) where C_(switch) is the capacitanceacross each switch, including both the transistor output capacitance andalso possible external capacitors placed in parallel with the switch,while n_(a)=1 for a full bridge and n_(a)=2 for a half bridge. For classD, one can also write the analytical expressions

F _(R)(dc)=sin² u/π,F _(X)(dc)=(u−sin u*cos u)/π,  (2)

where u=π(1-2*dc), indicating that the characteristic impedance level ofa class D amplifier decreases as the duty cycle, dc, increases towards50%. For a class D amplifier operation with dc=50%, achieving ZVS andZCS is possible only when the switching elements have practically nooutput capacitance (C_(a)=0) and the load is exactly on resonance(X_(o)=0), while R_(o) can be arbitrary.

Impedance Matching Networks

In applications, the driven load may have impedance that is verydifferent from the characteristic impedance of the external drivingcircuit, to which it is connected. Furthermore, the driven load may notbe a resonant network. An Impedance Matching Network (IMN) is a circuitnetwork that may be connected before a load as in FIG. 6B, in order toregulate the impedance that is seen at the input of the networkconsisting of the IMN circuit and the load. An IMN circuit may typicallyachieve this regulation by creating a resonance close to the drivingfrequency. Since such an IMN circuit accomplishes all conditions neededto maximize the power transmission efficiency from the generator to theload (resonance and impedance matching—ZVS and ZCS for a switchingamplifier), in embodiments, an IMN circuit may be used between thedriving circuit and the load.

For an arrangement shown in FIG. 6B, let the input impedance of thenetwork consisting of the Impedance Matching Network (IMN) circuit andthe load (denoted together from now on as IMN+load) beZ_(l)=R_(l)(ω)+jX_(l)(ω). The impedance matching conditions of thisnetwork to the external circuit with characteristic impedanceZ_(o)=R_(o)−jX_(o) are then R_(l)(ω)=R_(o), X_(l)(ω)=X_(o).

Methods for Tunable Impedance Matching of a Variable Load

In embodiments where the load may be variable, impedance matchingbetween the load and the external driving circuit, such as a linear orswitching power amplifier, may be achieved by using adjustable/tunablecomponents in the IMN circuit that may be adjusted to match the varyingload to the fixed characteristic impedance Z, of the external circuit(FIG. 6B). To match both the real and imaginary parts of the impedancetwo tunable/variable elements in the IMN circuit may be needed.

In embodiments, the load may be inductive (such as a resonator coil)with impedance R+jωL, so the two tunable elements in the IMN circuit maybe two tunable capacitance networks or one tunable capacitance networkand one tunable inductance network or one tunable capacitance networkand one tunable mutual inductance network.

In embodiments where the load may be variable, the impedance matchingbetween the load and the driving circuit, such as a linear or switchingpower amplifier, may be achieved by using adjustable/tunable componentsor parameters in the amplifier circuit that may be adjusted to match thecharacteristic impedance Z_(o) of the amplifier to the varying (due toload variations) input impedance of the network consisting of the IMNcircuit and the load (IMN+load), where the IMN circuit may also betunable (FIG. 6C). To match both the real and imaginary parts of theimpedance, a total of two tunable/variable elements or parameters in theamplifier and the IMN circuit may be needed. The disclosed impedancematching method can reduce the required number of tunable/variableelements in the IMN circuit or even completely eliminate the requirementfor tunable/variable elements in the IMN circuit. In some examples, onetunable element in the power amplifier and one tunable element in theIMN circuit may be used. In some examples, two tunable elements in thepower amplifier and no tunable element in the IMN circuit may be used.

In embodiments, the tunable elements or parameters in the poweramplifier may be the frequency, amplitude, phase, waveform, duty cycleand the like of the drive signals applied to transistors, switches,diodes and the like.

In embodiments, the power amplifier with tunable characteristicimpedance may be a tunable switching amplifier of class D, E, F or anycombinations thereof. Combining Equations (1) and (2), the impedancematching conditions for this network are

R _(l)(ω)=F _(R)(dc)/ωC _(a) ,X _(l)(ω)=F _(X)(dc)/ωC _(a)  (3).

In some examples of a tunable switching amplifier, one tunable elementmay be the capacitance C_(a), which may be tuned by tuning the externalcapacitors placed in parallel with the switching elements.

In some examples of a tunable switching amplifier, one tunable elementmay be the duty cycle dc of the ON switch-state of the switchingelements of the amplifier. Adjusting the duty cycle, dc, via Pulse WidthModulation (PWM) has been used in switching amplifiers to achieve outputpower control. In this specification, we disclose that PWM may also beused to achieve impedance matching, namely to satisfy Eq. (3), and thusmaximize the amplifier efficiency.

In some examples of a tunable switching amplifier one tunable elementmay be the switching frequency, which is also the driving frequency ofthe IMN+load network and may be designed to be substantially close tothe resonant frequency of the IMN+load network. Tuning the switchingfrequency may change the characteristic impedance of the amplifier andthe impedance of the IMN+load network. The switching frequency of theamplifier may be tuned appropriately together with one more tunableparameters, so that Eqs. (3) are satisfied.

A benefit of tuning the duty cycle and/or the driving frequency of theamplifier for dynamic impedance matching is that these parameters can betuned electronically, quickly, and over a broad range. In contrast, forexample, a tunable capacitor that can sustain a large voltage and has alarge enough tunable range and quality factor may be expensive, slow orunavailable for with the necessary component specifications

Examples of Methods for Tunable Impedance Matching of a Variable Load

A simplified circuit diagram showing the circuit level structure of aclass D power amplifier 802, impedance matching network 804 and aninductive load 806 is shown in FIG. 8. The diagram shows the basiccomponents of the system with the switching amplifier 804 comprising apower source 810, switching elements 808, and capacitors. The impedancematching network 804 comprising inductors and capacitors, and the load806 modeled as an inductor and a resistor.

An exemplary embodiment of this inventive tuning scheme comprises ahalf-bridge class-D amplifier operating at switching frequency f anddriving a low-loss inductive element R+jωL via an IMN, as shown in FIG.8.

In some embodiments L′ may be tunable. L′ may be tuned by a variabletapping point on the inductor or by connecting a tunable capacitor inseries or in parallel to the inductor. In some embodiments C_(a) may betunable. For the half bridge topology, C_(a) may be tuned by varyingeither one or both capacitors C_(switch), as only the parallel sum ofthese capacitors matters for the amplifier operation. For the fullbridge topology, C_(a) may be tuned by varying either one, two, three orall capacitors C_(switch), as only their combination (series sum of thetwo parallel sums associated with the two halves of the bridge) mattersfor the amplifier operation.

In some embodiments of tunable impedance matching, two of the componentsof the IMN may be tunable. In some embodiments, L′ and C₂ may be tuned.Then, FIG. 9 shows the values of the two tunable components needed toachieve impedance matching as functions of the varying R and L of theinductive element, and the associated variation of the output power (atgiven DC bus voltage) of the amplifier, for f=250 kHz, dc=40%, C_(a)=640pF and C₁=10 nF. Since the IMN always adjusts to the fixedcharacteristic impedance of the amplifier, the output power is alwaysconstant as the inductive element is varying.

In some embodiments of tunable impedance matching, elements in theswitching amplifier may also be tunable. In some embodiments thecapacitance C_(a) along with the IMN capacitor C₂ may be tuned. Then,FIG. 10 shows the values of the two tunable components needed to achieveimpedance matching as functions of the varying R and L of the inductiveelement, and the associated variation of the output power (at given DCbus voltage) of the amplifier for f=250 kHz, dc=40%, C₂=10 nF andωL′=1000Ω. It can be inferred from FIG. 10 that C₂ needs to be tunedmainly in response to variations in L and that the output powerdecreases as R increases.

In some embodiments of tunable impedance matching, the duty cycle dcalong with the IMN capacitor C₂ may be tuned. Then, FIG. 11D shows thevalues of the two tunable parameters needed to achieve impedancematching as functions of the varying R and L of the inductive element,and the associated variation of the output power (at given DC busvoltage) of the amplifier for f=250 kHz, C_(a)=640 pF, C₂=10 nF andωL′=1000Ω. It can be inferred from FIG. 11D that C₂ needs to be tunedmainly in response to variations in L and that the output powerdecreases as R increases.

In some embodiments of tunable impedance matching, the capacitance C_(a)along with the IMN inductor L′ may be tuned. Then, FIG. 11A shows thevalues of the two tunable components needed to achieve impedancematching as functions of the varying R of the inductive element, and theassociated variation of the output power (at given DC bus voltage) ofthe amplifier for f=250 kHz, dc=40%, C₂=10 nF and C₂=7.5 nF. It can beinferred from FIG. 11A that the output power decreases as R increases.

In some embodiments of tunable impedance matching, the duty cycle dcalong with the IMN inductor L′ may be tuned. Then, FIG. 11B shows thevalues of the two tunable parameters needed to achieve impedancematching as functions of the varying R of the inductive element, and theassociated variation of the output power (at given DC bus voltage) ofthe amplifier for f=250 kHz, C_(a)=640 pF, C₂=10 nF and C₂=7.5 nF asfunctions of the varying R of the inductive element. It can be inferredfrom FIG. 11B that the output power decreases as R increases.

In some embodiments of tunable impedance matching, only elements in theswitching amplifier may be tunable with no tunable elements in the IMN.In some embodiments the duty cycle dc along with the capacitance C_(a)may be tuned. Then, FIG. 11C, shows the values of the two tunableparameters needed to achieve impedance matching as functions of thevarying R of the inductive element, and the associated variation of theoutput power (at given DC bus voltage) of the amplifier for f=250 kHz,C₁=10 nF, C₂=7.5 nF and ωL′=1000Ω. It can be inferred from FIG. 11C thatthe output power is a non-monotonic function of R. These embodiments maybe able to achieve dynamic impedance matching when variations in L (andthus the resonant frequency) are modest.

In some embodiments, dynamic impedance matching with fixed elementsinside the IMN, also when L is varying greatly as explained earlier, maybe achieved by varying the driving frequency of the external frequency f(e.g. the switching frequency of a switching amplifier) so that itfollows the varying resonant frequency of the resonator. Using theswitching frequency f and the switch duty cycle dc as the two variableparameters, full impedance matching can be achieved as R and L arevarying without the need of any variable components. Then, FIG. 12 showsthe values of the two tunable parameters needed to achieve impedancematching as functions of the varying R and L of the inductive element,and the associated variation of the output power (at given DC busvoltage) of the amplifier for C_(a)=640 pF, C₂=10 nF, C₂=7.5 nF andL′=637 μH. It can be inferred from FIG. 12 that the frequency f needs tobe tuned mainly in response to variations in L, as explained earlier.

Tunable Impedance Matching for Systems of Wireless Power Transmission

In applications of wireless power transfer the low-loss inductiveelement may be the coil of a source resonator coupled to one or moredevice resonators or other resonators, such as repeater resonators, forexample. The impedance of the inductive element R+jωL may include thereflected impedances of the other resonators on the coil of the sourceresonator. Variations of R and L of the inductive element may occur dueto external perturbations in the vicinity of the source resonator and/orthe other resonators or thermal drift of components. Variations of R andL of the inductive element may also occur during normal use of thewireless power transmission system due to relative motion of the devicesand other resonators with respect to the source. The relative motion ofthese devices and other resonators with respect to the source, orrelative motion or position of other sources, may lead to varyingcoupling (and thus varying reflected impedances) of the devices to thesource. Furthermore, variations of R and L of the inductive element mayalso occur during normal use of the wireless power transmission systemdue to changes within the other coupled resonators, such as changes inthe power draw of their loads. All the methods and embodiments disclosedso far apply also to this case in order to achieve dynamic impedancematching of this inductive element to the external circuit driving it.

To demonstrate the presently disclosed dynamic impedance matchingmethods for a wireless power transmission system, consider a sourceresonator including a low-loss source coil, which is inductively coupledto the device coil of a device resonator driving a resistive load.

In some embodiments, dynamic impedance matching may be achieved at thesource circuit. In some embodiments, dynamic impedance matching may alsobe achieved at the device circuit. When full impedance matching isobtained (both at the source and the device), the effective resistanceof the source inductive element (namely the resistance of the sourcecoil R_(s) plus the reflected impedance from the device) isR=R_(s)√{square root over (1+U_(sd) ²)}. (Similarly the effectiveresistance of the device inductive element is R_(d)√{square root over(1+U_(sd) ²)}, where R_(d) is the resistance of the device coil.)Dynamic variation of the mutual inductance between the coils due tomotion results in a dynamic variation of U_(sd)=ωM_(sd)√{square rootover (R_(s)R_(d))}. Therefore, when both source and device aredynamically tuned, the variation of mutual inductance is seen from thesource circuit side as a variation in the source inductive elementresistance R. Note that in this type of variation, the resonantfrequencies of the resonators may not change substantially, since L maynot be changing. Therefore, all the methods and examples presented fordynamic impedance matching may be used for the source circuit of thewireless power transmission system.

Note that, since the resistance R represents both the source coil andthe reflected impedances of the device coils to the source coil, inFIGS. 9-12, as R increases due to the increasing U, the associatedwireless power transmission efficiency increases. In some embodiments,an approximately constant power may be required at the load driven bythe device circuitry. To achieve a constant level of power transmittedto the device, the required output power of the source circuit may needto decrease as U increases. If dynamic impedance matching is achievedvia tuning some of the amplifier parameters, the output power of theamplifier may vary accordingly. In some embodiments, the automaticvariation of the output power is preferred to be monotonicallydecreasing with R, so that it matches the constant device powerrequirement. In embodiments where the output power level is accomplishedby adjusting the DC driving voltage of the power generator, using animpedance matching set of tunable parameters which leads tomonotonically decreasing output power vs. R will imply that constantpower can be kept at the power load in the device with only a moderateadjustment of the DC driving voltage. In embodiments, where the “knob”to adjust the output power level is the duty cycle dc or the phase of aswitching amplifier or a component inside an Impedance Matching Network,using an impedance matching set of tunable parameters which leads tomonotonically decreasing output power vs. R will imply that constantpower can be kept at the power load in the device with only a moderateadjustment of this power “knob”.

In the examples of FIGS. 9-12, if R_(s)=0.19Ω, then the rangeR=0.2-2Ωcorresponds approximately to U_(sd)=0.3-10.5. For these values,in FIG. 14, we show with dashed lines the output power (normalized to DCvoltage squared) required to keep a constant power level at the load,when both source and device are dynamically impedance matched. Thesimilar trend between the solid and dashed lines explains why a set oftunable parameters with such a variation of output power may bepreferable.

In some embodiments, dynamic impedance matching may be achieved at thesource circuit, but impedance matching may not be achieved or may onlypartially be achieved at the device circuit. As the mutual inductancebetween the source and device coils varies, the varying reflectedimpedance of the device to the source may result in a variation of boththe effective resistance R and the effective inductance L of the sourceinductive element. The methods presented so far for dynamic impedancematching are applicable and can be used for the tunable source circuitof the wireless power transmission system.

As an example, consider the circuit of FIG. 14, where f=250 kHz,C_(a)=640 pF, R_(s)=0.19Ω, L_(s)=100 μH, C_(1s)=10 nF, ωL′_(s)=1000Ω,R_(d)=0.3Ω, L_(d)=40 μH, C_(1d)=87.5 nF, C_(2d)=13 nF, ωL′_(d)=400Ω andZ_(l)=50Ω, where s and d denote the source and device resonatorsrespectively and the system is matched at U_(sd)=3. Tuning the dutycycle dc of the switching amplifier and the capacitor C_(2s) may be usedto dynamically impedance match the source, as the non-tunable device ismoving relatively to the source changing the mutual inductance M betweenthe source and the device. In FIG. 14, we show the required values ofthe tunable parameters along with the output power per DC voltage of theamplifier. The dashed line again indicates the output power of theamplifier that would be needed so that the power at the load is aconstant value.

In some embodiments, tuning the driving frequency f of the sourcedriving circuit may still be used to achieve dynamic impedance matchingat the source for a system of wireless power transmission between thesource and one or more devices. As explained earlier, this methodenables full dynamic impedance matching of the source, even when thereare variations in the source inductance L_(s) and thus the sourceresonant frequency. For efficient power transmission from the source tothe devices, the device resonant frequencies must be tuned to follow thevariations of the matched driving and source-resonant frequencies.Tuning a device capacitance (for example, in the embodiment of FIG. 13C_(1d) or C_(2d)) may be necessary, when there are variations in theresonant frequency of either the source or the device resonators. Infact, in a wireless power transfer system with multiple sources anddevices, tuning the driving frequency alleviates the need to tune onlyone source-object resonant frequency, however, all the rest of theobjects may need a mechanism (such as a tunable capacitance) to tunetheir resonant frequencies to match the driving frequency.

Resonator Thermal Management

In wireless energy transfer systems, some portion of the energy lostduring the wireless transfer process is dissipated as heat. Energy maybe dissipated in the resonator components themselves. For example, evenhigh-Q conductors and components have some loss or resistance, and theseconductors and components may heat up when electric currents and/orelectromagnetic fields flow through them. Energy may be dissipated inmaterials and objects around a resonator. For example, eddy currentsdissipated in imperfect conductors or dielectrics surrounding or near-bythe resonator may heat up those objects. In addition to affecting thematerial properties of those objects, this heat may be transferredthrough conductive, radiative, or convective processes to the resonatorcomponents. Any of these heating effects may affect the resonator Q,impedance, frequency, etc., and therefore the performance of thewireless energy transfer system.

In a resonator comprising a block or core of magnetic material, heat maybe generated in the magnetic material due to hysteresis losses and toresistive losses resulting from induced eddy currents. Both effectsdepend on the magnetic flux density in the material, and both can createsignificant amounts of heat, especially in regions where the fluxdensity or eddy currents may be concentrated or localized. In additionto the flux density, the frequency of the oscillating magnetic field,the magnetic material composition and losses, and the ambient oroperating temperature of the magnetic material may all impact howhysteresis and resistive losses heat the material.

In embodiments, the properties of the magnetic material such as the typeof material, the dimensions of the block, and the like, and the magneticfield parameters may be chosen for specific operating power levels andenvironments to minimize heating of the magnetic material. In someembodiments, changes, cracks, or imperfections in a block of magneticmaterial may increase the losses and heating of the magnetic material inwireless power transmission applications.

For magnetic blocks with imperfections, or that are comprised of smallersize tiles or pieces of magnetic material arranged into a larger unit,the losses in the block may be uneven and may be concentrated in regionswhere there are inhomogeneities or relatively narrow gaps betweenadjacent tiles or pieces of magnetic material. For example, if anirregular gap exists in a magnetic block of material, then the effectivereluctance of various magnetic flux paths through the material may besubstantially irregular and the magnetic field may be more concentratedin portions of the block where the magnetic reluctance is lowest. Insome cases, the effective reluctance may be lowest where the gap betweentiles or pieces is narrowest or where the density of imperfections islowest. Because the magnetic material guides the magnetic field, themagnetic flux density may not be substantially uniform across the block,but may be concentrated in regions offering relatively lower reluctance.Irregular concentrations of the magnetic field within a block ofmagnetic material may not be desirable because they may result in unevenlosses and heat dissipation in the material.

For example, consider a magnetic resonator comprising a conductor 1506wrapped around a block of magnetic material composed of two individualtiles 1502, 1504 of magnetic material joined such that they form a seam1508 that is perpendicular to the axis of the conductor 1506 loops asdepicted in FIG. 15. An irregular gap in the seam 1508 between the tilesof magnetic material 1502, 1504 may force the magnetic field 1512(represented schematically by the dashed magnetic field lines) in theresonator to concentrate in a sub region 1510 of the cross section ofthe magnetic material. Since the magnetic field will follow the path ofleast reluctance, a path including an air gap between two pieces ofmagnetic material may create an effectively higher reluctance path thanone that traverses the width of the magnetic material at a point wherethe pieces of magnetic materials touch or have a smaller air gap. Themagnetic flux density may therefore preferentially flow through arelatively small cross area of the magnetic material resulting in a highconcentration of magnetic flux in that small area 1510.

In many magnetic materials of interest, more inhomogeneous flux densitydistributions lead to higher overall losses. Moreover, the moreinhomogeneous flux distribution may result in material saturation andcause localized heating of the area in which the magnetic flux isconcentrated. The localized heating may alter the properties of themagnetic material, in some cases exacerbating the losses. For example,in the relevant regimes of operation of some materials, hysteresis andresistive losses increase with temperature. If heating the materialincreases material losses, resulting in more heating, the temperature ofthe material may continue to increase and even runaway if no correctiveaction is taken. In some instances, the temperature may reach 100 C ormore and may degrade the properties of the magnetic material and theperformance of wireless power transfer. In some instances, the magneticmaterials may be damaged, or the surrounding electronic components,packaging and/or enclosures may be damaged by the excessive heat.

In embodiments, variations or irregularities between tiles or pieces ofthe block of magnetic material may be minimized by machining, polishing,grinding, and the like, the edges of the tiles or pieces to ensure atight fit between tiles of magnetic materials providing a substantiallymore uniform reluctance through the whole cross section of the block ofmagnetic material. In embodiments, a block of magnetic material mayrequire a means for providing a compression force between the tiles toensure the tiles are pressed tight together without gaps. Inembodiments, an adhesive may be used between the tiles to ensure theyremain in tight contact.

In embodiments the irregular spacing of adjacent tiles of magneticmaterial may be reduced by adding a deliberate gap between adjacenttiles of magnetic material. In embodiments a deliberate gap may be usedas a spacer to ensure even or regular separations between magneticmaterial tiles or pieces. Deliberate gaps of flexible materials may alsoreduce irregularities in the spacings due to tile movement orvibrations. In embodiments, the edges of adjacent tiles of magneticmaterial may be taped, dipped, coated, and the like with an electricalinsulator, to prevent eddy currents from flowing through reducedcross-sectional areas of the block, thus lowering the eddy currentlosses in the material. In embodiments a separator may be integratedinto the resonator packaging. The spacer may provide a spacing of 1 mmor less.

In embodiments, the mechanical properties of the spacer between tilesmay be chosen so as to improve the tolerance of the overall structure tomechanical effects such as changes in the dimensions and/or shape of thetiles due to intrinsic effects (e.g., magnetostriction, thermalexpansion, and the like) as well as external shocks and vibrations. Forexample, the spacer may have a desired amount of mechanical give toaccommodate the expansion and/or contraction of individual tiles, andmay help reduce the stress on the tiles when they are subjected tomechanical vibrations, thus helping to reduce the appearance of cracksand other defects in the magnetic material.

In embodiments, it may be preferable to arrange the individual tilesthat comprise the block of magnetic material to minimize the number ofseams or gaps between tiles that are perpendicular to the dipole momentof the resonator. In embodiments it may be preferable to arrange andorient the tiles of magnetic material to minimize the gaps between tilesthat are perpendicular to the axis formed by the loops of a conductorcomprising the resonator.

For example, consider the resonator structure depicted in FIG. 16. Theresonator comprises a conductor 1604 wrapped around a block of magneticmaterial comprising six separate individual tiles 1602 arranged in athree by two array. The arrangement of tiles results in two tile seams1606, 1608 when traversing the block of magnetic material in onedirection, and only one tile seam 1610 when traversing the block ofmagnetic material in the orthogonal direction. In embodiments, it may bepreferable to wrap the conductor wire 1604 around the block of magneticmaterial such that the dipole moment of the resonator is perpendicularto the fewest number of tile seams. The inventors have observed thatthere is relatively less heating induced around seams and gaps 1606,1608 that are parallel to the dipole moment of the resonator. Seams andgaps that run perpendicular to the dipole moment of the resonator mayalso be referred to as critical seams or critical seam areas. It maystill be desirable, however, to electrically insulate gaps that runparallel to the dipole moment of the resonator (such as 1606 and 1608)so as to reduce eddy current losses. Uneven contact between tilesseparated by such parallel gaps may cause eddy currents to flow throughnarrow contact points, leading to large losses at such points.

In embodiments, irregularities in spacing may be tolerated with adequatecooling of the critical seam areas to prevent the localized degradationof material properties when the magnetic material heats up. Maintainingthe temperature of the magnetic material below a critical temperaturemay prevent a runaway effect caused by a sufficiently high temperature.With proper cooling of the critical seam area, the wireless energytransfer performance may be satisfactory despite the additional loss andheating effects due to irregular spacing, cracks, or gaps between tiles.

Effective heat sinking of the resonator structure to prevent excessivelocalized heating of the magnetic material poses several challenges.Metallic materials that are typically used for heatsinks and thermalconduction can interact with the magnetic fields used for wirelessenergy transfer by the resonators and affect the performance of thesystem. Their location, size, orientation, and use should be designed soas to not excessively lower the perturbed Q of the resonators in thepresence of these heatsinking materials. In addition, owing to therelatively poor thermal conductivity of magnetic materials such asferrites, a relatively large contact area between the heatsink and themagnetic material may be required to provide adequate cooling which mayrequire placement of substantial amount of lossy materials close to themagnetic resonator.

In embodiments, adequate cooling of the resonator may be achieved withminimal effect on the wireless energy transfer performance withstrategic placement of thermally conductive materials. In embodiments,strips of thermally conductive material may be placed in between loopsof conductor wire and in thermal contact with the block of magneticmaterial.

One exemplary embodiment of a resonator with strips of thermallyconductive material is depicted in FIG. 17. FIG. 17A shows the resonatorstructure without the conducting strips and with the block of magneticmaterial comprising smaller tiles of magnetic material forming gaps orseams. Strips of thermally conductive 1708 material may be placed inbetween the loops of the conductor 1702 and in thermal contact with theblock of magnetic material 1704 as depicted in FIGS. 17B and 17C. Tominimize the effects of the strips on the parameters of the resonator,in some embodiments it may be preferable to arrange the strips parallelto the loops of conductor or perpendicular to the dipole moment of theresonator. The strips of conductor may be placed to cover as much or asmany of the seams or gaps between the tiles as possible especially theseams between tiles that are perpendicular to the dipole moment of theresonator.

In embodiments the thermally conductive material may comprise copper,aluminum, brass, thermal epoxy, paste, pads, and the like, and may beany material that has a thermal conductivity that is at least that ofthe magnetic material in the resonator (˜5 W/(K-m) for some commercialferrite materials). In embodiments where the thermally conductivematerial is also electrically conducting, the material may require alayer or coating of an electrical insulator to prevent shorting anddirect electrical contact with the magnetic material or the loops ofconductor of the resonator.

In embodiments the strips of thermally conductive material may be usedto conduct heat from the resonator structure to a structure or mediumthat can safely dissipate the thermal energy. In embodiments thethermally conductive strips may be connected to a heat sink such as alarge plate located above the strips of conductor that can dissipate thethermal energy using passive or forced convection, radiation, orconduction to the environment. In embodiments the system may include anynumber of active cooling systems that may be external or internal to theresonator structure that can dissipate the thermal energy from thethermally conducting strips and may include liquid cooling systems,forced air systems, and the like. For example, the thermally conductingstrips may be hollow or comprise channels for coolant that may be pumpedor forced through to cool the magnetic material. In embodiments, a fielddeflector made of a good electrical conductor (such as copper, silver,aluminum, and the like) may double as part of the heatsinking apparatus.The addition of thermally and electrically conducting strips to thespace between the magnetic material and the field deflector may have amarginal effect on the perturbed Q, as the electromagnetic fields inthat space are typically suppressed by the presence of the fielddeflector. Such conducting strips may be thermally connected to both themagnetic material and the field deflector to make the temperaturedistribution among different strips more homogeneous.

In embodiments the thermally conducting strips are spaced to allow atleast one loop of conductor to wrap around the magnetic material. Inembodiments the strips of thermally conductive material may bepositioned only at the gaps or seams of the magnetic material. In otherembodiments, the strips may be positioned to contact the magneticmaterial at substantially throughout its complete length. In otherembodiments, the strips may be distributed to match the flux densitywithin the magnetic material. Areas of the magnetic material which undernormal operation of the resonator may have higher magnetic fluxdensities may have a higher density of contact with the thermallyconductive strips. In embodiments depicted in FIG. 17A) for example, thehighest magnetic flux density in the magnetic material may be observedtoward the center of the block of magnetic material and the lowerdensity may be toward the ends of the block in the direction of thedipole moment of the resonator.

To show how the use of thermally conducting strips helps to reduce theoverall temperature in the magnetic material as well as the temperatureat potential hot spots, the inventors have performed a finite elementsimulation of a resonator structure similar to that depicted in FIG.17C. The structure was simulated operating at a frequency of 235 kHz andcomprising a block of EPCOS N95 magnetic material measuring 30 cm×30cm×5 mm excited by 10 turns of litz wire (symmetrically placed at 25 mm,40 mm, 55 mm, 90 mm and 105 mm from the plane of symmetry of thestructure) carrying 40 A of peak current each, and thermally connectedto a 50 cm×50 cm×4 mm field deflector by means of three 3×¾×1′ hollowsquare tubes (⅛″ wall thickness) of aluminum (alloy 6063) whose centralaxes are placed at −75 mm, 0 mm, and +75 from the symmetry plane of thestructure. The perturbed Q due to the field deflector and hollow tubeswas found to be 1400 (compared to 1710 for the same structure withoutthe hollow tubes). The power dissipated in the shield and tubes wascalculated to be 35.6 W, while that dissipated in the magnetic materialwas 58.3 W. Assuming the structure is cooled by air convection andradiation and an ambient temperature of 24° C., the maximum temperaturein the structure was 85° C. (at points in the magnetic materialapproximately halfway between the hollow tubes) while the temperature inparts of the magnetic material in contact with the hollow tubes wasapproximately 68° C. By comparison, the same resonator without thethermally conducting hollow tubes dissipated 62.0 W in the magneticmaterial for the same excitation current of 40 W peak and the maximumtemperature in the magnetic material was found to be 111° C.

The advantage of the conducting strips is more apparent still if weintroduce a defect in a portion of the magnetic material that is in goodthermal contact with the tubes. An air gap 10 cm long and 0.5 mm placedat the center of the magnetic material and oriented perpendicular to thedipole moment increases the power dissipated in the magnetic material to69.9 W (the additional 11.6 W relative to the previously discussedno-defect example being highly concentrated in the vicinity of the gap),but the conducting tube ensures that the maximum temperature in themagnetic material has only a relative modest increase of 11° C. to 96°C. In contrast, the same defect without the conducting tubes leads to amaximum temperature of 161° C. near the defect. Cooling solutions otherthan convection and radiation, such as thermally connecting theconducting tubes body with large thermal mass or actively cooling them,may lead to even lower operational temperatures for this resonator atthe same current level.

In embodiments thermally conductive strips of material may be positionedat areas that may have the highest probability of developing cracks thatmay cause irregular gaps in the magnetic material. Such areas may beareas of high stress or strain on the material, or areas with poorsupport or backing from the packaging of the resonator. Strategicallypositioned thermally conductive strips may ensure that as cracks orirregular gaps develop in the magnetic material, the temperature of themagnetic material will be maintained below its critical temperature. Thecritical temperature may be defined as the Curie temperature of themagnetic material, or any temperature at which the characteristics ofthe resonator have been degraded beyond the desired performanceparameters.

In embodiments the heastsinking structure may provide mechanical supportto the magnetic material. In embodiments the heatsinking structure maybe designed to have a desired amount of mechanical give (e.g., by usingepoxy, thermal pads, and the like having suitable mechanical propertiesto thermally connect different elements of the structure) so as toprovide the resonator with a greater amount of tolerance to changes inthe intrinsic dimensions of its elements (due to thermal expansion,magnetostriction, and the like) as well as external shocks andvibrations, and prevent the formation of cracks and other defects.

In embodiments where the resonator comprises orthogonal windings wrappedaround the magnetic material, the strips of conducting material may betailored to make thermal contact with the magnetic material within areasdelimited by two orthogonal sets of adjacent loops. In embodiments astrip may contain appropriate indentations to fit around the conductorof at least one orthogonal winding while making thermal contact with themagnetic material at least one point. In embodiments the magneticmaterial may be in thermal contact with a number of thermally conductingblocks placed between adjacent loops. The thermally conducting blocksmay be in turn thermally connected to one another by means of a goodthermal conductor and/or heatsinked.

Throughout this description although the term thermally conductivestrips of material was used as an exemplary specimen of a shape of amaterial it should be understood by those skilled in the art that anyshapes and contours may be substituted without departing from the spiritof the inventions. Squared, ovals, strips, dots, elongated shapes, andthe like would all be within the spirit of the present invention.

Communication in a Wireless Energy Transfer System

A wireless energy transfer system may require a verification step toensure that energy is being transferred from a designated source to adesignated device. In a wireless energy transfer system, a source and adevice do not require physical contact and may be separated by distancesof centimeters or more. In some configurations with multiple sources ormultiple devices that are within the wireless power transfer range ofone another it may be necessary to determine or verify the source anddevice that are transferring power between each other.

Verification of an energy transfer may be important when an out-of-bandcommunication channel is used in the wireless energy transfer system. Anout-of-band communication channel may be used to transfer data betweendifferent components of the wireless energy transfer system.Communication between a source and a device or between multiple devices,sources, and the like may be used to coordinate the wireless energytransfer or to adjust the parameters of a wireless energy transfersystem to optimize efficiency, power delivery, and the like.

In some embodiments all of the signaling and communication may beperformed using an in-band communication channel that uses the samefields as are used for energy transfer. Using only the in-bandcommunication channel may have the advantage of not requiring a separateverification step. In some embodiments however, a separate out-of-bandcommunication channel may be more desirable. An out-of-bandcommunication channel may be less expensive and support higher datarates. An out-of-band communication channel that does not use near-fieldcommunication may support longer distance allowing resonator discovery.Likewise a separate out-of-band communication channel may not requirepower to be applied to the resonators and communication and likewisecommunication may occur without disruption of the power transfer.

An out-of-band communication channel is a channel that does not use themagnetic fields used for energy transfer by the resonators. Thecommunication channel may use a separate antenna and a separatesignaling protocol that is disjoint from the energy transfer resonatorand magnetic fields. An out of band communication channel that does notuse the resonator or modulate the fields used for energy transfer mayhave a different range or effective distance than the effective oruseful energy transfer range of the system. An of out-band communicationchannel may use or be based on Bluetooth, WiFi, Zigbee technology andthe like and may be effective over several or even several hundred ormore meters while the wireless energy transfer may have an effectiverange of several or even 30 or more centimeters. This difference inrange, performance, or capability may affect the coordination of thewireless energy transfer system.

For example, consider the arrangement of a wireless energy system shownin FIG. 18 comprising a two device resonators 1802, 1816 each with anout-of-band communication module 1804, 1818 respectively and two sourceresonators 1806, 1810 each with their own out-of-band communicationmodules 1808, 1812 respectively. The system may use the out-of-bandcommunication channel to adjust and coordinate the energy transfer. Thecommunication channel may be used to discover or find resonators in theproximity, to initiate power transfer, and to communicate adjustment ofoperating parameters such as power output, impedance, frequency, and thelike of the individual resonators.

In some situations the device resonator may incorrectly communicate withone source but receive energy from another source resonator. Thedisparity between the energy transfer channel and the communicationchannel may create performance, safety, and reliability issues since thecommunication that is used to coordinate the energy transfer, i.e.communicate operating point adjustment of the resonators, may have noeffect on the parameters of the wireless energy transfer channel.

In one instance a device resonator 1802 may be in close proximity withstrong coupling to only one of the source resonators 1806 as shown inFIG. 18 with weak coupling to the other source resonator 1810 that islocated further away from the device resonator 1802. In some instances,due to interference, obstruction, and the like the out-of-bandcommunication signal may be not functioning for the source 1806 anddevice 1802 pair with the stronger coupling between the resonators usedfor energy transfer than for a source 1810 and device 1802 pair with theweaker coupling between the resonators. If another device 1816 initiateswireless energy transfer with the source 1806 the device 1802 mayreceive power from a source in close proximity 1806 while having an outof band communication channel 1814 with a source 1810 that is furtheraway. Any attempt by the device 1802 to adjust the energy transfer willtherefore by unsuccessful since the device 1802 does not havecommunication with the source from which it is receiving energy.

Due to this disconnect between the communication and control channel andthe energy transfer channel other system level reliability and controlproblems may develop and may lead to security and stabilityvulnerabilities. There may be a need for a separate verification step ofthe wireless energy transfer channel. As those skilled in the art willrecognize the example is just but one example that illustrates the needbut many configurations and arrangements of the system may benefit froman explicitly or implicitly energy transfer verification step.

In embodiments, these potential problems may be avoided by providing anadditional verification step that ensures that the energy transferchannel and the communication channels are used by a source or a deviceare associated with the same external source or device.

In embodiments the verification step may comprise information exchangeor signaling of through the wireless energy transfer channel. Averification step comprising communication or information exchange usingthe energy transfer channel, or fields of the energy transfer channelmay be used to verify the corresponding accuracy of the out-of-bandcommunication channel.

In embodiments with an out-of-band communication channel theverification step may be implicit or explicit. In some embodimentsverification may be implicit. In embodiments an energy transfer channelmay be implicitly verified by monitoring and comparing the behavior ofthe energy transfer channel to expected behavior or parameters inresponse to the out-of-band information exchange. An energy transferchannel may be implicitly verified by monitoring the behavior andparameters of the energy transfer channel in response to the out-of-bandcommunication. For example, after an out-of-band communication exchangewhich is expected to increase energy transfer the parameters of thewireless energy transfer channel and resonators used for the wirelessenergy transfer may be monitored. An observed increase of deliveredpower at the device may used to infer that the out-of-band communicationchannel and the energy transfer channel are correctly identified.

In embodiments an implicit verification step may involve monitoring anynumber of the parameters of the wireless energy transfer or parametersof the resonators and components used in the wireless energy transfer.In embodiments the currents, voltages, impedance, frequency, efficiency,temperature, and the like may be monitored and compared to expectedvalues, trends, changes and the like as a result of an out-of-bandcommunication exchange.

In embodiments a source or a device unit may keep a table of measuredparameters and expected values, trends, changes, to these parameters asa consequence of a communication exchange. A source of a device maystore a history of communications and observed parameter changes thatmay be used to verify the energy transfer channel. In some cases asingle unexpected parameter change due to a communication exchange maybe not be conclusive enough to determine is the out-of-band channel isincorrectly paired. In some embodiments the history of parameter changesmay be scanned or monitored over several or many communication exchangesto perform verification.

An example algorithm showing the series of steps which may be used toimplicitly verify an energy transfer channel in a wireless energytransfer system using out-of-band communication is shown in FIG. 19A. Inthe first step 1902 an out-of-band communication channel between asource and a device is established. In the next step 1904 the source anddevice may exchange information as regarding adjusting the parameters ofthe wireless energy transfer or parameters of the components used forwireless energy transfer. The information exchange on the out-of-bandcommunication channel may be a normal exchange used in normal operationof the system to control and adjust the energy transfer. In some systemsthe out-of-band communication channel may be encrypted preventingeavesdropping, impersonation, and the like. In the next step 1906 thesource and the device or just a source or just a device may monitor andkeep track of any changes to the parameters of the wireless energytransfer or any changes in parameters in the components used in theenergy transfer. The tracked changes may be compared against expectedchanges to the parameters as a consequence of any out-of-bandcommunication exchanges. Validation may be considered failed when one ormany observed changes in parameters do not correspond to expectedchanges in parameters.

In some embodiments of wireless energy transfer systems verification maybe explicit. In embodiments a source or a device may alter, dither,modulate, and the like the parameters of the wireless energy transfer orthe parameters of the resonators used in the wireless energy transfer tocommunicate or provide a verifiable signal to a source or device throughthe energy transfer channel. The explicit verification may involvechanging, altering, modulating, and the like some parameters of thewireless energy transfer or the parameters of the resonators andcomponents used in the energy transfer for the explicit purpose ofverification and may not be associated with optimizing, tuning, oradjusting the energy transfer.

The changing, altering, modulating, and the like some parameters of thewireless energy transfer or the parameters of the resonators andcomponents used in the energy transfer for the purpose of signaling orcommunicating another wireless energy resonator or component may bereferred to as in-band communication. In-band communication may becharacterized by its use of the fields or structures used for energytransfer. In embodiments, the in-band communication channel may beimplemented as part of the wireless energy transfer resonators andcomponents by modulating the parameters of the magnetic fields or theresonators used for wireless energy transfer. Information may betransmitted from one resonator to another by changing the parameters ofthe resonators. Parameters such as inductance, impedance, resistance,and the like may be dithered or changed by one resonator. These changesin impedance may affect the impedance, resistance, or inductance ofother resonators around the signaling resonator. The changes maymanifest themselves as corresponding dithers of voltage, current, andthe like on the resonators which may be detected and decoded intomessages. In embodiments in-band communication may involve altering,changing, modulating, and the like the power level, frequency, and thelike of the magnetic fields used for energy transfer.

In one embodiment the explicit in-band verification may be performedafter an out-of-band communication channel has been established. Usingthe out-of-band communication channel a source and a device may exchangeinformation as to the power transfer capabilities and in-band signalingcapabilities. Wireless energy transfer between a source and a device maythen be initiated. The source or device may request or challenge theother source or device to signal using the in-band communication channelto verify the connection between the out-of-band and communicationchannel and the energy transfer channel. The channel is verified whenthe agreed signaling established in the out-of-band communicationchannel is observed at the in-band communication channel.

In embodiments verification may be performed only during specific orpre-determined times of an energy protocol such as during energytransfer startup. In other embodiments explicit verification step may beperformed periodically during the normal operation of the wirelessenergy transfer system. The verification step may be triggered when theefficiency or characteristics of the wireless power transfer changewhich may signal that the physical orientations have changed. Inembodiments the communication controller may maintain a history of theenergy transfer characteristic and initiate a verification of thetransfer that includes signaling using the resonators when a change inthe characteristics is observed. A change in the energy transfercharacteristics may be observed in the efficiency of the energytransfer, in the impedance, voltage, current, and the like of theresonators, or components of the resonators and power and controlcircuitry.

Those skilled in the art will appreciate a signaling and communicationchannel capable of transmitting messages may be secured with any numberof encryption, authentication, and security algorithms. In embodimentsthe out-of-band communication may be encrypted and the securedcommunication channel may be used to transmit random sequences forverification in the in-band channel. In embodiments the in-bandcommunication channel may be encrypted, randomized, or secured by anyknown security and cryptography protocols and algorithms. The securityand cryptography algorithms may be used to authenticate and verifycompatibility between a source and device and may use a public keyinfrastructure (PKI) and secondary communication channels forauthorization and authentication.

In embodiments of energy transfer system between a source and a device adevice may verify the energy transfer channel to ensure it is receivingenergy from the desired or assumed source. A source may verify theenergy transfer channel to ensure energy is being transferred to thedesired or assumed source. In some embodiments the verification may bebidirectional and a source and device may both verify their energytransfer channels in one step or protocol operation.

An example algorithm showing the series of steps which may be used toexplicitly verify an energy transfer channel in a wireless energytransfer system using out-of-band communication is shown in FIG. 19B. Inthe first step 1908 an out-of-band communication channel between asource and a device is established. In the next step 1910 the source anddevice may coordinate or agree on a signaling protocol, method, scheme,and the like that may be transmitted through the wireless energytransfer channel. To prevent eavesdropping and provide security theout-of-band communication channel may be encrypted and the source anddevice may follow any number of known cryptographic authenticationprotocols. In a system enabled with cryptographic protocols theverification code may comprise a challenge-response type exchange whichmay provide an additional level of security and authenticationcapability. A device, for example, may challenge the source to encrypt arandom verification code which it sends to the source via theout-of-band communication channel using a shared secret encryption keyor a private key. The verification code transmitted in the out-of-bandcommunication channel may then be signaled 1912 through the in-bandcommunication channel. In the case where the source and device areenabled with cryptographic protocols the verification code signaled inthe in-band communication channel may be encrypted or modified by thesender with a reversible cryptographic function allowing the receiver tofurther authenticate the sender and verify that the in-bandcommunication channels are linked with the same source or deviceassociated with the out-of-band communication channel.

In situations when the verification fails a wireless energy transfersystem may try to retry validation. In some embodiments the system maytry to re-validate the wireless energy transfer channel by exchanginganother verification sequence for resignaling using the in-bandcommunication channel. In some embodiments the system may change oralter the sequence or type of information that is used to verify thein-band communication channel after attempts to verify the in-bandcommunication channel have failed. The system may change the type ofsignaling, protocol, length, complexity and the like of the in-bandcommunication verification code.

In some embodiments, upon failure of verification of the in-bandcommunication channel and hence the energy transfer channel, the systemmay adjust the power level, the strength of modulation, frequency ofmodulation and the like of the signaling method in the in-bandcommunication channel. For example, upon failure of verification of asource by a device the system may attempt to perform the verification ata higher energy transfer level. The system may increase the power outputof the source generating stronger magnetic fields. In another example,upon failure of verification of a source by a device the source thatcommunicated the verification code to the device by changing theimpedance of its source resonator may increase or even double the amountof change in the impedance of the source resonator for the signaling.

In embodiments upon failure of verification of the energy transferchannel the system my try to probe, find, or discover other possiblesources or devices using the out-of-band communication channel. Inembodiments the out-of-band communication channel may be used to findother possible candidates for wireless energy transfer. In someembodiments the system may change or adjust the output power or therange of the out-of-band communication channel to help minimize falsepairings.

The out-of-band communication channel may be power modulated to haveseveral modes, long range mode to detect sources and a short range orlow power mode to ensure the communication is with an another device orsource that is in close proximity. In embodiments the out-of-bandcommunication channel may be matched to the range of the wirelesschannel for each application. After failure of verification of theenergy transfer channel the output power of the out-of-bandcommunication channel may be slowly increased to find other possiblesources or devices for wireless energy transfer. As discussed above, anout-of-band communication channel may exhibit interferences andobstructions that may be different from the interferences andobstructions of the energy transfer channel and sources and devices thatmay require higher power levels for out-of-band communication may be inclose enough proximity to allow wireless energy transfer.

In some embodiments the out-of-band communication channel may bedirected, arranged, focused using shielding or positioning to be onlyeffective in a confined area (i.e., under a vehicle). to ensure it isonly capable of establishing communication with another source or devicethat is in close enough proximity, position, and orientation for energytransfer.

In embodiments the system may use one or more supplemental sources ofinformation to establish an out-of-band communication channel or toverify an in-band energy transfer channel. For example, during initialestablishment of an out-of-band communication channel the locations ofthe sources or devices may be compared to known or mapped locations or adatabase of locations of wireless sources or devices to determine themost probable pair for successful energy transfer. Out-of-bandcommunication channel discovery may be supplemented with GPS data from aGPS receiver, data from positioning sensors and the like.

Photovoltaic (PV) Panels with Wireless Energy Transfer

We describe a system that may use a source resonator, and a captureresonator, to wirelessly transfer power from an exterior solar PV panelto an interior capture module or to other solar PV panels. Inembodiments a solar PV panel has one or more resonators that transferthe solar generated power from the solar PV panel to one or moreresonators that may be part of another solar PV panel, or may be insidea building, vehicle, boat, and the like, or part of a mounting structureof the panel.

In embodiments one or more resonators may be integrated into the solarPV panel assembly. Resonators may be integrated into the perimeter ofthe panel or they may be designed to fit under the photovoltaic elementof the panel. The resonators may be designed and oriented to generate amagnetic field that is substantially perpendicular to the plane of thePV panel to allow efficient coupling with resonators that may be placedbehind the panel. In embodiments the integrated resonators in the PVpanel may be designed and positioned such that the magnetic field issubstantially parallel to the surface of the panel allowing efficientcoupling with like resonators that are on the sides of the panel. Inother embodiments resonators may be designed and oriented to generate amagnetic field that is substantially omnidirectional. In embodimentswith integrated resonators, no physical or direct electrical contactsare required.

FIG. 20 shows a diagram of a rectangular PV panel 2002 with outlines ofthree integrated resonators showing several possible resonatororientations and locations. A resonator may be integrated into theperimeter 2001 of the panel. Resonators may be placed inside the orbehind the PV panel in any location 2003 and may have various sizes andorientations such as the resonator 2004 which is oriented such that themagnetic field is directed out of the corner of the panel. Although notshown in the figure, the resonators may include appropriate shieldingand magnetic field guides to reduce perturbations and loses from theresonators.

In embodiments a resonator of the PV panel may be outside of the mainpanel body assembly. A cable or a wired connector may attach the PVpanel to the resonator. In this embodiment the location and orientationof the resonator may be chosen and altered independently of the positionof the PV panel and may allow more flexibility in mounting andpositioning of the system. In this embodiment the resonator of the PVpanel may be aligned with the receiving resonator without having to movethe PV panel. FIG. 21 shows an embodiment of a PV panel 2103 with anexternal resonator 2101 that is wired 2102 to the PV panel.

In embodiments a PV panel may contain more than one resonator. A PVpanel may contain one or more internal resonators and may have one ormore external resonators. The resonators may be aligned and positionedin different orientations to allow energy transfer to resonators placesin various orientations and positions relative to the PV panel. Inembodiments multiple resonators of the PV panel may be usedsimultaneously to transfer and receive power from other resonators. Forexample, one resonator of a PV panel may be used to receive power fromanother PV panel and use one of its other resonators to transfer powerto a device or a resonator inside a building. A PV panel system mayemploy various panel designs each with possibly different resonatorconfigurations.

In panels with integrated resonators the panels may not require anyholes, feedthroughs, wiring, or connectors. Electronics that control thePV panel and the resonators may all be integrated into the panel. Thepanel can thus be made completely enclosed and waterproof providingcomplete protection against moisture, dust, dirt, insects, and the like.In some embodiments the enclosure of the PV panel may preferably becomposed partially or completely of magnetically permeable materials toallow efficient magnetic coupling and minimize losses in the energytransfer. In some embodiments, magnets may be used to hold PV panelscomprising magnetically permeable materials in place. The PV panels maybe of any size, shape, and dimension and are not limited to thegeometries pictured. Resonators and PV panels may be of any geometry,for example they may be shaped to follow the contours of a vehicle.Resonators and PV panels may be flexible or hinged and may be designedsuch that they can be rolled into a tube or folded when not in use.

In accordance with the presence invention power may be wirelesslytransferred from the PV panel resonators to resonators powering devicesor to resonators that are coupled to the electrical network of abuilding, vehicle, and the like.

In one embodiment, PV panels with resonators may be used to directly andwirelessly power devices. Devices capable of coupling to the magneticresonators of the PV panels can wirelessly receive energy to power theirelectronics or recharge batteries. Device resonators can be tuned tocouple to the resonators of the PV panels. PV panels with integrated orexternal resonators for wireless power transfer may be deployed in manyenvironments and applications. The PV panel may be attached or placedeither permanently or temporarily on vehicles, buildings, tool boxes,planes, and other structures to provide wireless power from solarenergy. With wireless power transfer no wiring is required to connectdevices to the PV panel and hence the PV panel can be easily installedor placed in areas that require power.

For example, as shown in FIG. 22 a PV panel with the described wirelesspower transfer resonators may be attached to the roof 2202, trunk 2203,side panel 2204, or hood 2201 of a vehicle. The energy from the PV panelmay be wirelessly transferred through the roof, trunk, side panel, orhood of the vehicle by the resonator of the PV panel into the vehicle topower or charge electronics within the vehicle. Devices with resonatorscan directly couple to the resonator of the PV panel and receive power.Devices such as mobile handsets, laptops, gaming consoles, GPS devices,electric tools, and the like can be charged or power wirelessly byenergy derived from solar power despite the devices being in a dark,enclosed space of a vehicle without requiring wiring. PV panels withwireless power transfer may be attached to the top or above the bed of apick-up truck for example, allowing wireless charging of batteries orbattery powered tools that may be stored in the back of the truck.

In another example, PV panels may be mounted on the exterior of a car. Acapture resonator inside the vehicle, under the roof, the hood, or thetrunk of the vehicle that is coupled to the electrical system of thevehicle can capture the energy from the resonator of the PV panel. Thesolar energy can be used to power the vehicle, recharge batteries, orpower other peripherals of the vehicle. With wireless power transfer thePV panels can be installed or retrofitted to the vehicle without havingto make any hard-wired connections between the panel and the vehiclesimplifying the installation and allowing quick removal if necessary.

In another example, PV panels with wireless power transmission may beintegrated into the top of an awning or a sun umbrella as shown in FIG.23. PV panels on top of an umbrella 2303, 2304, 2305, 2306 with internalor external resonators may transfer power to enabled devices such aslaptops 2302 or mobile handsets 2301 that are located the shade belowthe umbrella or awning.

In other embodiments, PV panels with wireless power transfer may be usedtransfer power to a resonator that is directly coupled to a wired powerdistribution or electrical system of a house, vehicle, and the likewithout requiring any direct contact between the exterior PV panels andthe internal electrical system. For example, a solar PV panel with theabove described resonators may be mounted directly onto the exterior ofa building, vehicle, and the like. A resonator may be mounted inside thebuilding, vehicle, and the like which can be connected to the electricalsystem of the structure. The resonator on the interior can receive powerfrom the PV panels on the exterior and transfer the energy to theelectrical system of the structure allowing powering of devicesconnected to the power system. In embodiments, the power received by theresonator from the PV panels can be conditioned in a way that allows itto be transferred to the electrical grid. For example, one or morecapture resonators may provide electrical power to an inverter, saidinverter then providing power to the electrical grid.

For example, as shown in a diagram in FIG. 24, PV panels with wirelesspower transfer may be mounted on the exterior roof of a building. Aresonator that is coupled to the electrical system of the building maybe mounted on the interior underside of the roof behind the PV panel.Power may be transferred from the exterior PV panel to the interiorelectrical system of the building without requiring any drilling orpenetration of the exterior of the building for wiring. Solar power fromthe PV panels may then be utilized by electric devices connected to thewired electrical system of the building. Captured electrical energy fromthe PV panels may also be provided to a breaker panel which may beattached to the electrical grid.

PV panels with wireless power transfer may simplify installation andconnection of multiple PV panels. Wireless power transfer may beutilized for connection and capture power from several PV panels thatmay be part of a system.

In one embodiment with multiple PV panels, each panel may have one ormore resonators that transmit power to a device or to a correspondingresonator that is coupled to a wired electric system. PV panels placedon the exterior roof of a building, for example, may each have acorresponding capture resonator on the interior of the building that iscoupled to electrical system. PV panels placed on the exterior of a car,for example, may each power couple to various device resonators insidethe vehicle. In such embodiments each PV panel is independent of otherPV panels. A diagram of an example rooftop configuration of such asystem is shown in FIG. 25. Each PV panel 2502 in the figure hasresonators 2503 that can transmit energy directly through the roof 2501to a resonator mounted inside the building (not shown).

In another embodiment with multiple PV panels, the panels may utilizewireless power transfer between each other to transfer or collect powerto/from one or more of designated panels. In this embodiment only a fewdesignated panels are able to transmit power to devices or resonatorsthat are coupled to an electrical system. The energy is gathered andtransmitted in one or several points. In such embodiments adjacent PVpanels are dependent on each other, but may be easily installed orreplaced when faulty since no wiring between panels or electrical systemis required. A diagram of an example rooftop configuration of such asystem is shown in FIG. 26. One or more panels 2606 have resonators 2605that can transfer energy to a resonator inside the building. Energy fromother resonators may be transferred wirelessly from panel to panel untilit reaches the panel that is capable of transmitting the energy into thebuilding. For example in FIG. 26, panel 2601 may transfer energy to itsadjacent panel 2602 via their coupled resonators 2607, 2608. Likewisepanel 2602 may transfer its energy and the energy from panel 2601 topanel 2606 via coupled resonators 2603, 2604. Panel 2606 may thentransfer the energy originating from panels 2601, 2602, 2606 to aresonator inside the building (not shown).

In another embodiment with multiple PV panels, an additional connectionstructure that wirelessly receives power from multiple panels can beused. A structure of resonators may be mounted into a mounting stripthat is placed beneath or next to PV panels. Resonators of the PV panelmay wirelessly transfer their energy to the resonators on the strip. Oneor a few resonators connected to the strip can be used to transfer thepower from all the panels to devices or to an interior resonator coupledto an electronic system. In such a system, once a resonator strip isinstalled panels may be removed or added to the system by securing thepanels on or near the connection structure. A diagram of an examplerooftop configuration of such a system is shown in FIG. 27. A structureof resonators 2702, shaped as a flat elongated strip may be attached tothe roof of a building. A PV panel 2701 with a resonator 2703 maytransfer energy to the strip. The strip may then use a single resonator2705 that is coupled to a resonator inside the building (not shown) totransfer the energy of all the panels to the interior without any wires.A panel may be added or removed from the system by simply placing thepanel on top of the strip.

In yet another embodiment multiple panels can be physically wiredtogether to a resonator that can transmit their power wirelessly todevices wired or coupled to other resonators on the interior of abuilding or vehicle.

With all of the above configurations using wireless power transfer,significantly simpler installation of PV panels is possible becausepower may be transmitted wirelessly from the panel to a captureresonator in the building or vehicle, eliminating all outside wiring,connectors, and conduits, and any holes through the roof or walls of thestructure. Wireless power transfer used with solar cells may have abenefit in that it can reduced roof danger since it eliminates the needfor electricians to work on the roof to interconnect panels, strings,and junction boxes. Installation of solar panels integrated withwireless power transfer may require less skilled labor since fewerelectrical contacts need to be made. Less site specific design may berequired with wireless power transfer since the technology gives theinstaller the ability to individually optimize and position each solarPV panel, significantly reducing the need for expensive engineering andpanel layout services.

With wireless power transfer, PV panels may be deployed temporarily, andthen moved or removed, without leaving behind permanent alterations tothe surrounding structures. They may be placed out in a yard on sunnydays, and moved around to follow the sun, or brought inside for cleaningor storage, for example. For backyard or mobile solar PV applications,an extension cord with a wireless energy capture device may be thrown onthe ground or placed near the solar unit. The capture extension cord canbe completely sealed from the elements and electrically isolated, sothat it may be used in any indoor or outdoor environment.

With wireless power transfer no wires or external connections may benecessary to the PV solar panels and they can be completely weathersealed. Significantly improved reliability and lifetime of electricalcomponents in the solar PV power generation and transmission circuitrycan be expected since the weather-sealed enclosures can protectcomponents from UV radiation, humidity, weather, dust, and the like.With wireless power transfer and weather-sealed enclosures it may bepossible to use less expensive components since they will no longer bedirectly exposed to external factors and weather elements and it mayreduce the cost of PV panels. Likewise PV panels with wireless powertransfer can be more generic and more portable since the PV panels donot require a fixed hardwired connection.

In embodiments power transfer between the PV panels and the captureresonators inside a building or a vehicle may be bidirectional. Energymay be transmitted from the house grid to the PV panels to provide powerwhen the panels do not have enough energy for self calibration,alignment, or maintenance tasks. Reverse power flow can be used to powerheating elements that can melt snow from the panels, or power motorsthat will position the panels in a more favorable position with respectto the light source. Once the snow is melted or the panels arerepositioned energy can be transfer from the PV panels.

In some embodiments, the source electronics that are coupled to thesource resonator may comprise at least one half-bridge or full-bridgeswitching amplifier. The capture electronics that are coupled to thecapture resonator may comprise at least one half-bridge or full-bridgerectifier further comprising power transistors. These embodiments allowwireless power transfer from an energy source connected to the sourceelectronics to be delivered to a load connected to the captureelectronics. Note that both the source and capture electronics employhalf-bridge or full-bridge switching circuits. Therefore, theseembodiments also allow wireless power transfer in the reverse directionwhere an energy source that is connected to the capture electronics cantransfer energy to a load connected to the source electronics. Thisenables, for example, transferring and retrieving energy wirelessly froman energy storage medium such as a battery, fly wheel, capacitor,inductor, and the like. It also enables reverse power flow to awirelessly enabled PV panel for melting snow, as described above.

The resonators and the wireless power transfer circuitry may includetuning and safety mechanisms. In embodiments PV panels with wirelesspower transfer may include auto-tuning on installation to ensure maximumand efficient power transfer to the wireless collector. For example,variations in roofing materials or variations in distances between thePV panels and the wireless power collector in different installationsmay affect the performance or perturb the properties of the resonatorsof the wireless power transfer. To reduce the installation complexitythe wireless power transfer components may include a tuning capabilityto automatically adjust their operating point to compensate for anyeffects due to materials or distance. Frequency, impedance, capacitance,inductance, duty cycle, voltage levels and the like may be adjusted toensure efficient and safe power transfer.

The resonators and wireless power transfer circuitry may include tuningthat ensures maximum power extraction from the PV panels as well asefficient wireless transfer of the extracted power. In embodiments, thewireless power transfer circuitry may be configured for energy transferbetween resonators while also applying an equivalent load resistance toa PV panel for optimal energy extraction. Such a wireless source canefficiently transfer energy from a PV panel to a wireless capture deviceover a wider range of environmental conditions than is currentlypossible. For example, as the solar illumination level (or equivalentlyirradiance) increases during the morning, the impedance applied to theoutput of the PV panel would decrease in a manner that maximizes powerextraction from the PV panel. Such a wireless energy source is referredto herein as a “wireless energy maximum power point tracker (WEMPPT).”For example, FIG. 28A depicts a solar panel comprising a plurality ofphotovoltaic junctions connected in series. For simplicity, eachphotovoltaic junction is represented by the parallel combination of acurrent source and a diode. A more realistic model would include seriesand shunt resistances, diode variations, and the like. The voltage V andcurrent I generated by the panel depend, in part, on the solarirradiance, and on the equivalent resistance R presented to the outputof the panel. FIG. 28B shows several exemplary curves for parametricvariation of R and different solar illumination levels. Also depicted inFIG. 28B are the points on the curves where the maximum power can beextracted from the PV panel by a given load resistance R. This is thevalue of R that a maximum power point tracker (MPPT) should present tothe panel.

For the circuit model depicted in FIG. 28A, the current flowing into theresistance R is

${I_{solar} - {I_{s}( {^{\frac{V}{N\; V_{th}}} - 1} )}},$

where I_(solar) is the solar-generated current, V is the voltage acrossthe panel, N is the number of cells in the panel, I_(s) is the reversesaturation current, and V_(th) is approximately 0.026 V at a temperatureof 25 C. The power extracted from the panel that can be wirelesslytransferred is simply V×I_(solar). The root of the derivative of powerwith respect to V, results in the maximum power point voltage:

V _(MPPT) =NV _(th) [W(e(I _(solar) +I _(s))/I _(s))−1],  (4)

where W(z) is the Lambert W-function or product-log function, defined byinverse function for z=W(z) e^(W(z)). FIG. 29 shows a plot of themaximum power point voltage as a function of the PV panel or arraycurrent. For this example, the resistance for maximum power that shouldbe presented by the WEMPPT to the PV panel is the slope of the curveshown in FIG. 29. FIG. 30 shows this resistance and how it varies withsolar illumination for an exemplary panel with 60 cells, 1 m² area, androom temperature operation. For example, with 1 kW/m² irradiance, thearray current would be approximately 8 A and the optimum resistancewould be 4Ω. If the irradiance were to drop to 0.2 kW/m² then theoptimum resistance would be 12.5Ω. In one embodiment, a wireless powersource may only present a fixed resistance to the PV panel. A loss ofefficiency may then occur. For the example above, the efficiency at 0.2kW/m² irradiance would be more than a factor of four lower than for 1kW/m²—which would result in more than a factor of 20 reduction inextracted power. In another embodiment, using the WEMPPT configurationwould preserve the efficiency for the irradiances in the example so thatthe extracted power is substantially proportional to the solarirradiance.

In embodiments, a wireless energy source can be connected to the outputof a conventional MPPT circuit that may include a DC-to-DC converter andthat is connected to a PV panel. FIG. 31A shows one such embodiment. Inthis embodiment loss of system efficiency may occur because of powerdissipation in both the MPPT circuit and the wireless energy source.FIG. 31B shows a more efficient embodiment where a wireless energysource can mimic the behavior of a separate MPPT circuit withoutincurring the additional efficiency loss of a separate MPPT circuit.FIG. 31C shows another embodiment where a wireless energy capturecircuit provides efficient wireless energy capture as well as acontrolled output level of current or voltage. In embodiments, such acircuit, labeled “Rectifier with DC current or voltage conversion” inFIG. 31 C, can be realized with a half-bridge or full-bridge switchingcircuit. In embodiments, the rectifier adjusts the duty cycle and/or thephase angle of the PWM waveform in the device (and/or the source) toaffect wireless energy capture and voltage or current regulation. Therectifier may also adjust the switching times of the switches relativeto the oscillating current flowing through the device resonator toefficiently capture wireless energy and also maintain voltage or currentcontrol.

PV panels with WEMPPTs may simplify installation of strings of panelswhere different panels in the string experience different levels ofirradiance or different environmental conditions. Strings ofseries-connected PV panels are useful for developing higher outputvoltage than a single panel can provide. A high output voltage may bemore compatible with load devices such as grid-tied inverters, off-gridinverters, charge controllers for battery chargers, and the like. Inembodiments, a plurality of PV panels, each with an associated WEMPPT,may be placed on a roof top or other external surface and exposed toillumination of varying levels between panels. Under the roof or at theinternal surface, a plurality of energy capture devices may receivewireless energy from the sources and have their outputs combined. FIG.32 depicts an embodiment where the outputs of device resonators 3224,3226, 3228, 3230, 3232 receiving wireless energy from source resonatorsof the PV cells 3202, 3204, 3206, 3208, 3210 are combined into a stringunder the roof. In embodiments, the outputs of the capture devices arecombined in series to boost the net voltage. In embodiments, the capturedevices include current or voltage regulation 3212, 3214, 3216, 3218,3220 and their outputs are combined in series to create a higher voltagewith a regulated current or voltage 3222. In embodiments, the capturedevices include current or voltage regulation 3212, 3214, 3216, 3218,3220 and their output are combined in parallel to create a highercurrent with a regulated current or voltage 3222.

In embodiments, WEMPPT configuration may be realized in a wirelessenergy source comprising a switching amplifier with automatic adjustmentof the phase angle of the switching times for the transistors in theamplifier. The relationship in time between when the switches are openedand when the current flowing through the switches changes direction iswhat determines one phase angle, herein referred to as φ. Another phaseangle, herein referred to as γ, describes the relationship between whenthe diodes shunting the switches conduct and when the switches areclosed. This provides two degrees of freedom for adjusting thecharacteristics of the energy source in a way that is advantageous bothfor energy extraction from a PV panel, and for efficient wirelesstransmission of said extracted energy. More specifically, the amplifierdepicted in FIG. 33 can present an optimum resistance R_(dc) to the PVpanel while simultaneously presenting a substantially matched AC outputimpedance to the impedance matching network (IMN). This allows theextracted energy to be efficiently transferred through the source loopto the device loop and through the device IMN and to the rectifier.

FIG. 34 shows an example of a half-bridge amplifier that can be used toprovide an optimum resistance R_(dc) to a PV panel. Exemplary waveformsfor such an amplifier are depicted in FIGS. 35A and 35B for twodifferent timing configurations for operating switches S1 and S2. FIG.35A shows an example of a timing configuration for realizinghigh-efficiency AC waveforms. Note how the switch S1 is closed at theprecise moment when the current i_(ac) changes sign and also when thevoltage v_(ac) reaches V_(dc)/2. While closing, the switch S1 is said toexperience zero-current and zero-voltage switching. A short time before,defined as φ/ω, the switch S2 was opened and experienced zero-voltageswitching. A half-period after S2 was opened, S1 opens and alsoexperiences zero-voltage switching. These conditions result in nearlyzero dissipation in the switches. The high-efficiency switching can berealized for different designs with various values of φ/ω, whileproviding a degree of freedom for impedance matching to various ac loadsfor wireless energy transmission. An additional degree of freedom isneeded to adjust the dc resistance presented to the PV panel. One suchdegree of freedom is depicted in FIG. 35B which shows how S2 can beopened slightly earlier than depicted in FIG. 35A. The value of v_(ac)then reaches V_(dc)/2 before S1 closes and the current i_(ac) then flowsthrough the diode D1 (turning it on) until the current crosses zero. Thediode D1 stays on for a time γ/ω at which time the switch S1 closesunder a nearly zero-voltage condition. Note that zero-current switchingis sacrificed, although near-zero-voltage switching is preserved becauseof the diodes. This still results in high-efficiency operation.Adjusting the value of γ/ω provides an additional degree of freedom foradjusting the dc resistance presented to the PV panel. FIG. 36 shows aspecific example of how the dc resistance can be changed by a factor of4 by adjusting the value of the phase γ for a fixed value of the phaseφ. For the circuit depicted in FIG. 34, an equation that relates the dcresistance to the phase γ can be written as

R _(dc)=(2π/ωC)(cos γ−cos(γ+φ))/(cos γ+cos(γ+φ)).  (5)

As the phase γ is adjusted, the AC output impedance of the amplifierchanges as well. FIG. 37A shows the dependence of the output impedanceon the phase φ. FIG. 37B shows how the output impedance additionallydepends on the phase γ. In embodiments, phases φ and γ are chosen incombinations that optimize R_(dc) presented to the PV panel as well asthe AC impedance presented to the impedance matching network. Inembodiments, the phase γ is adjusted in combination with circuitelements such as capacitors, inductors, and resistors in the impedancematching network to optimize R_(dc) presented to the PV panel as well asthe AC impedance presented to the source resonator.

In other embodiments, WEMPPT configurations may be realized in awireless energy source comprising circuit elements such as capacitors,inductors, and resistors by adding automatic adjustment of said circuitelements in response to changing environmental conditions. Said circuitelements may be part of any of the amplifier, impedance matchingnetwork, and/or resonator. In other embodiments, WEMPPT configurationsmay include circuit elements that can be tuned as well as switchingtimes for the transistors that can be adjusted. FIG. 38 depicts oneexemplary embodiment with a master control algorithm. The master controlalgorithm evaluates inputs such as the current and voltage waveformsflowing through the impedance matching network and source coilcombination. The algorithm uses processing of said inputs to determine,for example, a more optimal DC impedance to present to the PV celland/or a more favorable AC impedance to present to the impedancematching network. The algorithm controls a means of adjusting the PWMwaveform and/or a means of adjusting a tuning network so that the moreoptimal impedances may be realized.

FIG. 39 depicts an exemplary embodiment of a control algorithm. For atime-step n, the algorithm measures the AC voltage and current acrossthe impedance matching network. The algorithm also measures the DCvoltage across the PV panel. The algorithm then calculates a newsetpoint for a tunable capacitance in the tuning network and actuatesthe change. The voltages and currents are remeasured in a next time-stepand the adjustment loop continues until the desired capacitance state isachieved. Next, the power extracted from the PV panel is compared to thepower extracted in the previous time-step and the sign of the differenceis computed. The sign of the difference then determines how thealgorithm adjusts the duty cycle of the switching times of thetransistor switches. The duty cycle may be adjusted by changing eitherof the phase angles φ or γ, as described above.

In addition to solar PV panels, other methods of generating electricalenergy include wind-powered generators, water-powered generators,thermoelectric generators, thermophotovoltaic generators, and the like.Such methods also provide electrical output that varies withenvironmental conditions, and conventional MPPT circuits can be used tomaximize energy extraction. Those skilled in the art will understandthat the features of the WEMPPT configuration are general and may beapplied to a wide range of electrical energy generators.

In embodiments the wireless power transfer system may include safetyinterlocks and sensors. The PV panels and resonators may includetemperature, power, impedance, and voltage sensors and microcontrollersor processors to ensure the panel operates within allowable limits. Thewireless power transfer system may include a ground connection toprovide a discharge path for accumulated electric charge. The wirelesspower transfer system may include a voltage sensor that enablesdetection of accumulated electric charge. If no connection to earthground is available to the PV panel with wireless power transfer, thepanel may include a ground-fault interrupt sensor where the case of thePV panel is treated as ground.

In embodiments the PV panels and resonators may include sensors andvisual, auditory, and vibrational feedback to aid in resonator alignmentto ensure efficient power transfer between an external PV panel and aninternal capture resonator. For example, one of the resonators may beused to sense the position of another resonator by sensing an increaseor decrease in the resonant coupling between the resonators.Alternatively, an increase or decrease in the mutual inductance betweenthe resonators may be used to determine relative position of theresonators.

In embodiments with multiple PV panels or multiple resonators, theresonators of the system may be tuned to different frequencies to avoidinterference. The tuned frequency of the various resonators may be timeor frequency multiplexed. In other embodiments, the source and captureresonators may include a communications capability that allows thesource and capture resonators to exchange configuration information. Inother embodiments, such source and capture resonators may exchangeinformation needed for initial calibration or for verifying thatexchange of power is occurring between the intended resonators. Thecommunication can be in-band or out-of-band, as was described above.

FIG. 40 shows a preferred embodiment of the WEMPPT configuration for theexample of a solar PV panel installed on the roof of a building. A PVpanel is depicted at left as a series-connected plurality of solarcells, where each cell is represented by a simplified equivalent circuitcomprising a current source and a diode, as described above. Thecapacitor represents the capacitance across the PV panel terminals.Next, the PV panel terminals are connected to a full-bridge switchingamplifier that can operate in the class DE mode described above. Theswitching times for S1-S4 and related parameters such as duty cycle andthe phase angles φ and γ can be adjusted by a source controller. Next,the AC outputs of the switching amplifier are connected to an impedancematching network (IMN) with an adjustable circuit element such as acapacitor. As described herein, the combination of the switching timeparameters and the circuit element can be adjusted in a manner thatoptimizes both the extraction of power from the PV panel and thewireless transfer of power through the roof barrier for a variety ofenvironmental and solar irradiance conditions. A preferred algorithm formaking the adjustments uses measured values of at least one of the DCcurrent and DC voltage from the PV panel as well as measured values ofat least one of the AC current and AC voltage in the IMN or on thesource coil.

The right side of FIG. 40 shows the configuration of the power capturepart of the WEMPPT configuration-interior to the building in thisexample. An algorithm can be implemented in a capture controller thatperforms two functions. First, said controller optimizes the impedancematching of the capture coil to the rectifier. Second, said controllerregulates the DC current, DC voltage, and/or power output from therectifier. A preferred algorithm for the roof-top solar example measuresat least one of the AC current and AC voltage from the capture coil andat least one of the DC voltage or DC current from the rectifier. Theswitching times for S5-S8 can then be adjusted to maintainhigh-efficiency rectification. When coupled with another adjustableparameter such as a variable capacitor in the IMN, the switching timesand the variable capacitor can be adjusted to optimize impedancematching, maintain high-efficiency rectification, and regulate theoutput DC current or voltage or power from the rectifier.

In a preferred embodiment for the example of a plurality of PV panels ona roof, each PV panel may have a corresponding capture circuit whereeach capture circuit regulates its DC output current to a common valueI_(dc). Then the plurality of PV panels can be electrically connected inseries, as depicted in FIG. 41. Each PV panel may develop a voltageV_(dc) _(—) _(i), where i is an index corresponding to the ith PV panel.When different PV panels experience different irradiance, their powercapture circuits may develop different DC voltages at the common currentvalue of I_(dc). The sum of the different DC voltages, V_(string), isavailable to an inverter or battery charger. The amount of powersupplied to the inverter or charger is P−V_(string)×I_(dc). For a givenamount of power from the panels P, the value of V_(string) is determinedby the value of I_(dc) flowing through the series-connected capturecircuits. This is advantageous to maintaining a near-constant value ofV_(string) at the input of the inverter or charger—a condition thatallows the inverter or charger to operate near its peak efficiency. Torealize a near-constant V_(string), the inverter or charger may set thecommon current value L_(k) for each of the power capture circuits. Acommunications link could be established between the inverter or chargerand the power capture circuits to set the common current value. The linkcould make use of the DC wiring or it could use wireless communications.

The communications link could also be used to communicate information ofdiagnostic, performance, or other status information between theinverter or charger and the power capture circuits. It is also possiblefor each of the power capture circuits to obtain information about itscorresponding PV panel using either in-band or out-of-bandcommunications as described above. The information about the PV panelscan then be shared across the interior communications link. This couldinclude information about the relative alignment of a power capturecircuit with its corresponding PV panel. The relative alignment could bemonitored from the power capture circuit by a variety of techniquesincluding inductive sensing, magnetic field-strength sensing, capacitivesensing, thermal sensing, or other modalities that do not require roofpenetrations. In a preferred embodiment, relative alignment is monitoredwith a method that is sensitive to the mutual inductive coupling betweenthe source and capture coils.

Although described in the context of solar PV panels, one skilled in theart will appreciate that the techniques and methods described may beused with other energy harvesting devices such as wind turbines, waterturbines, thermal exchangers, and the like. An energy producing windturbine mounted on the roof of a building, for example, may benefit fromwireless power transfer in a similar way as described for the PV panels.Because other energy harvesting devices vary depending on environmentalconditions, the WEMPPT functionality described above may be used inembodiments other than PV panels. Power from the wind turbine may betransferred from the exterior to the interior of the building withouthaving to make holes or penetrations in the roof or walls. Likewisewater turbines in boats or other structures that use water motion likecurrents, waves, and the like to generate energy may benefit fromwireless power transfer. Drilling for wiring through a hull of a boat ora sealed submerged structure is undesirable for such applications. Withwireless power transmission, submerged turbines and energy harvestersmay be completely sealed and isolated making such devices more reliableand also easier to replace or repair since they can be removed andreplaced without requiring any resealing of connections.

Wireless Energy Transfer for Packaging

Wireless energy transfer may be used to transfer energy to productpackaging, packaged products, and the like. Power may be transferred topackaging or packaged products when the packages are on the shelves in aretail environment, in a storage environment, in a warehouseenvironment, in a refrigerator environment, in a shipping environment,and the like. Wireless energy captured by a package may be used toilluminate parts of the packaging, power electronics or sensors or thepackaging, control the temperature of the packaging, provide power todevices or batteries inside the packaging, provide power to displays onthe packaging, and the like.

Product packaging may include boxes, bags, bottles, stickers, cartons,displays, wrappings, bottle caps, signs, flyers, attachments, and thelike. Product packaging may be a disposable outer wrapper of a productthat gets removed before use. Product packaging may mean an integralpart of the product which does not get removed but is a permanent partof the product.

In accordance with exemplary and non-limiting embodiments, a deviceresonator and electronics may be integrated into the packaging, may belocated on the inside of the packaging, or attached to the outside ofthe packaging and receive wireless energy from a source resonatorlocated on a shelf, on a floor, in a ceiling, in a wall, and the like ata position to transfer energy from the source resonator to the deviceresonator.

In accordance with exemplary and non-limiting embodiments the energycaptured by the device resonator may be used to energize lights,buzzers, motors, vibrators, displays, organic materials, conductive inksor paints, or any other visual, auditory, or tactile stimulator that maybe used to enhance a product's appearance, to convey information, or toattract the attention of a consumer.

In accordance with exemplary and non-limiting embodiments, the energycaptured by the device resonator may be used directly by the packagedproduct. Energy may be used to recharge the battery of the packageddevice ensuring that when the device is purchased and unpacked thebattery of the device will be sufficiently charged for immediate use.

In accordance with exemplary and non-limiting embodiments, the energycaptured by the device resonator may be used to maintain or monitor theenvironmental conditions within the packaging. Parameters such astemperature, light, humidity, product freshness, product quality,packaging integrity, and the like may be monitored, recorded, andreported to a user or a consumer.

One exemplary embodiment of product packaging with a wireless energytransfer system is depicted in FIG. 42. A package 4202 with anintegrated device resonator 4208 and optional device electronics (notpictured) may be placed near a source resonator 4204 coupled to sourceelectronics (not pictured). The energy captured by the device resonatormay be used to energize a light emitting feature 4210 of the packagingvia a wired 4206 electrical connection. In embodiments the lightemitting feature may be an LED, a bulb, a fluorescent bulb, a lightemitting paint, a part of a display, and the like, that may be directlyattached, integrated and/or recessed in the packaging.

In accordance with exemplary and non-limiting embodiments, the sourceand device resonators 4204, 4208 may be of different sizes. Inaccordance with exemplary and non-limiting embodiments, it may bepreferable to have the source resonator 4204 be larger than the deviceresonator 4208 to allow a greater freedom of movement and placement ofthe device resonator 4208 within the proximity of the source resonator4204.

In accordance with exemplary and non-limiting embodiments, the sourceand device resonators 4204, 4208 may be of any resonator type describedherein and may include a planar resonator, a printed circuit boardresonator, and the like. In exemplary embodiments the coil of theresonators 4204, 4206 may be comprise an electrical conductor printeddirectly onto the packaging or onto an insert or a sticker that isattached to the packaging.

In accordance with exemplary and non-limiting embodiments, the deviceresonators 4208 may be adapted to fit into different sides and faces ofthe packaging. In accordance with exemplary and non-limitingembodiments, the device resonators 4208 may be adapted to fit roundpackaging such as depicted in FIG. 43 where a resonator coil 4316 isfitted around the perimeter of a cylindrical package 4314 and powers ailluminated logo 4312 of the package.

In embodiments the packaged products may be stacked or arranged inconfigurations where some packaged products may not be directly next toa source resonator 4204 but may be separated from a source resonator4204 by one or more other packages or products. To receive energy thepackaged products may need to receive energy through one or morepackaged products. For example, as depicted in FIG. 44 square packages4422 may be stacked in a three dimensional array on a shelf. The arraymay be four or more packages deep in all the directions. As a result, asource resonator 4204 placed on the top, back 4424, or bottom 4426 ofthe shelf 4428 may not be in contact or close proximity to all of thepackages in the array so as to provide energy to device resonators 4208corresponding to each of the packages 4422.

In accordance with exemplary and non-limiting embodiments, the maximumdimensions and distances of a stack or array of products may be limitedbased on the sizes of resonators, the power output from the sourceresonator, and the power requirements of the products. A package may berated for a maximum separation from the source and hence a maximumstacking height.

In accordance with exemplary and non-limiting embodiments, the stackingheight or separation distance of the source and the devices may beincreased with repeater resonators. Large repeater resonators may beplaced in between layers of stacked packaging increasing the couplingstrength of the resonators in the devices and the source. For example,for the configuration shown in FIG. 44, energized by the bottom sourceresonator 4426, a large repeater resonator 4430 may be inserted betweenthe first and the second layer of packages to extend the wireless energytransfer range to, for example, the second or third row of packages. Arepeater resonator 4430 may also be inserted between the second andthird rows and any additional rows.

In accordance with exemplary and non-limiting embodiments, the range ofwireless energy transfer and the stack height of packaged products maybe improved with a repeater resonator that is integrated or attached toeach package. A repeater resonator may be added to the package toimprove the coupling to the source resonator. An example of a packagewith a repeater resonator is depicted in FIG. 45. The package 4534includes a device resonator 4538 that provides energy to any electronicsor circuits in the packaging and a repeater resonator 4536 that may belarger than the device resonator and attached or integrated on the sameor different side or face of the package than the device resonator. Inthis configuration multiple packages may be stacked front to back with asource resonator in the back of the packages.

In accordance with exemplary and non-limiting embodiments, it may bedesirable to turn off or prevent energizing packages that may be in themiddle of a stack or to the back of a stack. For example, illuminating apackage designed to attract the attention of a consumer may only beuseful when the package is visible to the consumer. Packages that are inthe back of a stack may not be visible and energizing the packages maywaste energy, reduce the reliability of the circuits and potentiallylead to device failures. In embodiments the packages may be configuredto energize or turn on only when they are in front of a display or whenthey are visible to a consumer.

In accordance with exemplary and non-limiting embodiments, packages mayhave sensors, such as light sensors, RFID sensors and the like that maybe used to determine and activate the appropriate packaging.

In accordance with exemplary and non-limiting embodiments, the packagingmay be configured to selectively detune device resonators that are notin front of a display. A resonator detuned from the resonant frequencyof the source resonator may not efficiently receive energy from thesource and may be in effect be disabled. Selective detuning ofresonators may be accomplished by introducing a lossy material to matingfaces of packages when stacked together. A material such as a sheet ofan electrical conductor may sufficiently detune a device resonator whenbrought in close proximity to the device resonator. In embodimentspackaging may be designed with a small area of a lossy materialpositioned such that the lossy material may detune the device resonatorthat is not in the front of package stack.

For example, consider again the packaging 4534 depicted in FIG. 45comprising a device resonator 4538 and a repeater resonator 4536. Thepackaging may be designed to have a patch or sheet of a lossy material4540 on the opposite side of the device resonator such that when twopackages are stacked together the lossy material may load and detune thedevice resonator of the package in the back while not affecting therepeater resonator of each package allowing energy to pass through therepeater resonators to the front package.

A configuration with two packages is shown in FIG. 46. The configurationcomprises a source resonator 4646 and two packages 4643 and 4652 eachwith its own repeater resonator 4650, 4644 and device resonators 4654,4648 respectively. Each package may also have a patch of a lossymaterial 4656, 4658. The lossy material is positioned such that itaffects the device resonator of the box in back of it. For example, thepatch 4658 is positioned to detune the device resonator 4648 or the boxin the back without affecting the larger repeater resonators 4644, 4650,nor the device resonator of the front package 15854. Wireless energy maytherefore pass from the source resonator 4646 to the device resonator ofthe front box 4654 via the repeater resonator of the back box 4644without significantly energizing the device resonator 4648 of the backbox.

In embodiments, efficient energy transfer may be realized when the Q ofthe source and/or repeater resonators is relatively high and the Q ofthe device resonators incorporated into the packaging are relativelylow. Such lower Q resonators may comprise inductive elements comprisingprinted conductors, conducting inks, paints and the like. Inductiveelements that are easy to manufacture and safe to dispose of may bepreferable in packaging applications, even if the loss of these elementsis higher than electronics grade copper, as an example. Higher lossconductors comprising carbon traces and/or lower conductivity butprintable conductors may be suitable for this application becauseefficient power transfer may be realized using either or both higher Qsource and repeater resonators.

In embodiments, whole new marking and communication capabilities may berealizable using this inventive wireless power transfer scheme. Forexample, by enabling wireless power transfer to product packaging, thepackaging itself may include new functionality. For example, thepackaging may include communications functionality that allows thedisplayed price to be updated via a wireless communication link. In aretail environment, a package may communicate with the cell phone of aconsumer passing by, and cause the phone to ring or vibrate or emit aaudible tone to alert the consumer to the fact that the product is onspecial, or has been improved, or has been reviewed, etc. In a warehouseenvironment, a package may communicate with a centralized database sothat its location can be easily identified. For example, the UPS drivermay not need to scan his packages anymore because the packages will beable to communicate wirelessly with tracking software in the warehouse,in the truck, and may be further integrated with a GPS tracking schemeso that rather than just saying “on truck’”, a packaged could be trackedto the street location of the truck at a given time. Maybe the truckroute could be displayed along with a more accurate estimated arrivaltime.

Wireless communication functionality might also be used to form ad hocnetworks of multiple packages and the display capabilities or light-upcapabilities enabled by wireless power transfer may be further enhancedby creating synchronized displays involving multiple packages. Forexamples, the light-up functionality might be synchronized to create aflashing light display, or a display where the lights “run around thepackaging”. In addition to lights, wireless power may be used to poweraudible tones or to deliver marketing apps over a wireless link.

Wireless communication could be coupled with an “in-carriage” systemthat displays the cost of the contents of the carriage to the consumer.The carriage could have wireless power capability to supply power topackages in the cart. The carriage could be powered by rechargeablebatteries that are wirelessly recharged as the carriages sit at thecarriage stands or the carriages could be powered from source coils inthe floor as the carriages are pushed around a store. For fast sellingitems like the tickle me elmo or iphone, a consumer could download anapp on their phone that allows them to instantaneously get a count ofhow many products are available at any given store.

Wireless power apps could include maps of power sources, powermanagement and sharing, billing if you let someone have some of yourpower (their credit card could pay you before you share your power, oryou could choose to exchange it for free) it might happen without youeven knowing it. You could set your phone so that you always share powerwith a paying customer as long as you are at least 50% charged. Youcould also set your phone to be pinging for available power at a certainprice any time your charge state gets below a certain level. You couldset it to pay more for power when you reach a certain critical powerlevel. Apps might be coordinated with sales, coupons, etc informationthat is wirelessly transmitted by wirelessly powered devices. Apps mightlink certain products with recipes or consumer reviews or allow a userto comment or input data that could be made available for other appusers. Warnings could be displayed like spinach is currently suspectedto be the cause of an e. coli outbreak. Foods or products that need tobe recalled might be able to identify themselves on a shelf so that theycan be identified and removed by store employees or avoided byconsumers.

Wireless Software Modeling Tool

With reference to FIG. 47, there is illustrated an exemplary embodimentof a method for modeling parameters relevant to the design and operationof systems for the wireless transfer of power using magnetic resonance.Because of the multiplicity of parameters that may be adjusted toachieve a desirable system, particularly a system involving a sourceresonator and a device resonator, the mathematical computations requiredto arrive at a solution for the optimal or near optimal operation ofsuch a system may prove to be prohibitive. Specifically, as changes inany one parameter may affect the values of other related parameters thatmay in turn influence yet other parameter values, and so on, the abilityto arrive at a solution for the multi-dimensional problem spacecomprised of every possible combination of parameters and attendantparameter values may require unobtainable computational resources.

In accordance with various exemplary and non-limiting embodiments, theamount of computations required to arrive at a near optimal solution fora source and device resonator system operating in accordance withdesired, user specified parameter values is substantially reduced via amethod of separately modeling (1) the design of both the sourceresonator and device resonator and (2) the interaction between thesource resonator and device resonator. Specifically, it has beenobserved that the Q values of each of the source resonator and deviceresonator may be modeled separately while having little effect on thecoupling coefficient k between the source resonator and deviceresonator. Breaking down the modeling process to perform these two formsof modeling separately reduces the number of parameters required to bemodeled for either form individually. This reduces greatly the number ofcomputations required to be performed in both instances while theresults may be combined as described more fully below.

At step 4702, input parameters defining the attributes of at least onesource and device resonator, comprising at least one source coil and atleast one device coil, respectively, may be specified. Specifically,parameters corresponding to each of the at least one source coil and theat least one device coil may be specified individually. Then, at step4704, attributes defining both the source coil and the device coilvis-a-vis one another may be specified. Next, at step 4706, theelectromagnetic performance of the specified system comprising thesource resonator and the device resonator may be modeled with theresults used at step 4708 to design at least one impedance matchingnetwork (IMN). Note that the at least one source and the at least onedevice may comprise resonators, coils, and impedance matching networks.The impedance matching networks of the source and device may be designedto achieve certain system capabilities such as delivering a range ofpowers, maintaining a maximum output voltage, and/or open circuitvoltage, operating at a certain bus voltage, and the like. In thisdisclosure, it should be understood that, designing the impedancematching network, step 4708, may comprise designing an impedancematching network for a source and/or an impedance matching network for adevice. In some embodiments, the source and or device may have apredesigned, and/or pre-specified, impedance matching network, and thestep 4708, may be used to determine any remaining impedance matchingcircuits for the system. Lastly, the 4710 system thus modeled may bebuilt and operational parameters measured to be used as recursive inputsto step 4706 for incrementally improving the design of the system.

With reference to FIG. 48, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 4800 for entering sourcecoil design parameters. As illustrated, user-interface 4800 may bedisplayed in response to an activation of source coil design tab 4824.While the following examples make use of various graphical userinterface (GUI) elements, such as text entry fields, drop down menus andthe like, it is understood that any and all GUI elements may be utilizedto output and display data as well as to accept inputted data. Inembodiments, users of a software modeling tool may access the input andoutput paramaters using command lines, scripts, tables, links, and thelike. Such methods of inputting and outputting parameters and/or data tothe tool do not deviate from the methods, techniques, and embodimentsdescribed here.

As illustrated, global input panel 4802 may be comprised of a pluralityof entry fields that accept parameter values for the system as a wholeincluding, but not limited to, system units and an operating frequencyof the system. Source coil design panel 4804 may be comprised of aplurality of entry fields that accept parameter values defining a sourcecoil. As illustrated, a wire type entry field 4806 may comprise a dropdown menu for selecting a wire type such as, for example, litz wire,solid core wire, copper tubing, printed circuit board trace, and thelike, while wire attribute field 4808 may comprise a drop down menu formore specifically defining the physical dimensions of a selected wiretype.

Source coil type field 4810 may be a drop down menu for defining asource coil type. In the present example, a rectangular coil has beenchosen. Exemplary coil type attribute fields 4812 a-4812 e allow a userto input desired attribute values corresponding to the chosen sourcecoil type. For example, a rectangular source coil is in part defined bythe width and length of the rectangular source coil. As a result, coiltype attribute fields 4812 may be selectively displayed for receivinginputted width and length dimensions. Various other exemplary coil typeattribute fields include, but are not limited to, fields correspondingto source coil winding direction, source coil number of turns, andsource coil spacing between the turns.

Once defined via global input panel 4802 and source coil design panel4804, a source coil diagram 4814, such as a planimetric rendering, ofsource coil 4816 may displayed reflecting the chosen source coilattributes discussed above. In accordance with an exemplary embodiment,changes to any of the global input panel 4802 and source coil designpanel 4804 input fields may result in the real-time, or near real-time,updating of a source coil diagram 4814 to reflect such changes. Inanother exemplary embodiment, source coil diagram 4814 may be updated atthe request of a user such as via activation of update button 4818.

Once defined, a user may save a source coil 4816 design for laterretrieval and use such as in, for example, a parts library. Such savingof a source coil 4816 design may be achieved by activating, for example,a save button 4820. Likewise, previously saved or otherwise providedsource coil 4816 designs may be loaded for use or for furthermodification such as by, for example, activating a load button 4822.With reference to FIG. 49, there is illustrated an exemplary andnon-limiting embodiment of a user interface 4900 such as might bedisplayed in response to an activation of load button 4822.

As illustrated, each a plurality of groupings 4902 a, 4902 b eachcomprising one or more source coil designs 4904 may be displayed. In thepresent example groups 4902 a, 4902 b differ based upon frequencycharacteristics of the included source coil designs. Specifically, group4902 a is comprised of low-to-medium frequency source coil designs whilegroup 4902 b is comprised of high frequency source coil designs. In suchinstances, system 6400 operates to categorize saved source coil designsinto logical groupings for display based, at least in part, uponattributes of each source design coil such as those described above asinputted via a user interface 4800.

In accordance with another exemplary and non-limiting embodiment, searchinput fields may be provided as forming a part of user interface 4900 toallow a user to define one or more search characteristics. For example,a user may select, such as from one or more drop down menus, selectioncriteria comprising rectangular coils having a minimum width of 5 cm. Inresponse to such selection criteria, system 6400 may retrieve, such asfrom database in memory 6406, one or more source coil designs matchingthe specified search criteria. Once displayed, selection or activationof any source coil designs 4904 results in a return to user interface4800 whereby the entry fields of global input panel 4802 and source coildesign panel 4804 are filled in to reflect the retrieved attributevalues of the selected source coil design.

With reference to FIG. 50, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 5000 for entering devicecoil design parameters. As illustrated, user-interface 5000 may bedisplayed in response to an activation of device coil design tab 4824.

As illustrated, device coil design panel 5002 may be comprised of aplurality of entry fields that accept parameter values defining a devicecoil. As illustrated, wire type entry field 5004 comprises a drop downmenu for selecting a wire type such as, for example, litz wire whilewire attribute field 5006 comprises a drop down menu for morespecifically defining the physical dimensions of a selected wire type.Note the wire types and/or dimensions available for the design of adevice coil may be the same as those used in a source design or they maybe different.

Device coil type field 5008 may be a drop down menu for defining adevice coil type. In the present example, a rectangular coil has beenchosen. Exemplary coil type attribute fields 5010 a-5010 e may allow auser to input desired attribute values corresponding to the chosendevice coil type. For example, a rectangular device coil is in partdefined by the width and length of the rectangular device coil. As aresult, coil type attribute fields 5010 may be selectively displayed forreceiving inputted width and length dimensions. Various other exemplarycoil type attribute fields include, but are not limited to, fieldscorresponding to device coil winding direction, device coil number ofturns, and device coil spacing between the turns.

In embodiments, resonators may be formed by source coils and devicecoils having similar or identical parameters. In such instances, it maybe desirable to populate the fields of device coil design panel 5002with the parameters defined with respect to source coil design panel4804 (or vice versa). In accordance with an exemplary and non-limitingembodiment, a source design copy button 5012 may be provided and/or adevice design copy button (not shown) may be provided. Activating asource design copy button 5012 (or a device design copy button) resultsin the retrieval of attributes defining a corresponding source coil (ordevice coil) design. These retrieved attributes may be then utilized asa starting point from which, if desired, to further refine parametervalues defining the device coil (or source coil) design.

As before with reference to the source coil design of FIG. 48, a devicecoil diagram 5014, such as a planimetric rendering, of device coil 5016may be displayed reflecting the chosen device coil attributes discussedabove. In accordance with an exemplary embodiment, changes to any of thedevice coil design panel 5002 input fields may result in the real-time,or near real-time, updating of device coil diagram 5014 to reflect suchchanges. In another exemplary embodiment, device coil diagram 5014 maybe updated at the request of a user such as via activation of updatebutton 5018.

Once defined, a user may save a device coil design for later retrievaland use such as in, for example, a parts library. Such saving of adevice coil design may be achieved by activating, for example, savebutton 5018. Likewise, previously saved or otherwise provided devicecoil designs may be loaded for use or for further modification such asby, for example, activating load button 5020.

Once each of the source coil and the device coil forming a resonatorhave been defined as described above, attributes of the combined sourcecoil and device coil may be defined. With reference to FIG. 51 there isillustrated an exemplary and non-limiting embodiment of a user-interface5100 for entering source coil to device coil system design parametersUser interface 5100 may be accessed, for example, by selecting orotherwise activating coil-to-coil system design tab 5102.

In this exemplary embodiment, the device position and device orientationpanels 5104 enables the input of various positional parameters definingthe position and orientation of the device coil relative to the sourcecoil. For example, device position fields 5106 may allow for the entryof a desired coordinate system, such as a Cartesian coordinate system,for example, in which a position of the device coil relative to thesource coil may be specified as well as values defining the position ofthe device coil in the chosen coordinate system. Similarly, deviceorientation fields 5108 allow for the entry of a desired coordinatesystem, such as using Euler angle rotations, for example, in which anorientation of the device coil may be specified relative to the sourcecoil, as well as values defining the orientation of the device coil inthe chosen coordinate system.

Once the position and orientation of the device coil is defined, aresonator diagram 5110, such as a planimetric rendering, of theresonator comprising source coil 5114 and device coil 5112 may bedisplayed reflecting the chosen resonator coil attributes discussedabove. In accordance with an exemplary embodiment, changes to any of thedevice position and orientation panel 5104 input fields may result inthe real-time, or near real-time, updating of a resonator diagram 5110to reflect such changes. In another exemplary embodiment, a resonatordiagram 5110 may be updated at the request of a user such as viaactivation of update button 5116.

As described more fully below, an optional sweep parameter panel 5116may be provided. Sweep parameter panel 5116 may define a series ofdiscrete conditions under which the operation of the resonators is to becalculated, displayed, tested, and the like. In the present example,there is illustrated a situation wherein the distance, z, separating thesource coil and the device coil is to be varied from a minimum distanceof 1 cm to a maximum distance of 10 cm with calculations and/orpredictions of the response of the resonator calculated at ten evenlyspaced intervals between the minimum and maximum distance values. Notethat there are a wide range of swept parameters, combinations of sweptparameters, minimum and maximum values of swept parameters, ranges ofswept parameters, spacings of swept parameters and the like, that may berealized using a software modeling tool. The embodiment described hereis only a single exemplary embodiment.

There has therefore been described how various parameters defining thegeometry and composition of individual source coils and device coils aswell as resonators formed of a combination of a source coil and a devicecoil may be entered. In accordance with various exemplary andnon-limiting embodiments, system 6400 may further operate to performinput validation as user's enter parameters to define thecharacteristics of source coils, device coils and resonators asdescribed above. Specifically, system 6400 may operate to alert orprevent the occurrence of erroneous input field entries as well as theoccurrence of data field entries that are individually compliant but arelogically or physically inconsistent or incompatible with other inputfield entries.

With reference to FIG. 52, there is illustrated an instance of an errormessage according to an exemplary and non-limiting embodiment. In theexample illustrated, user interface 5200 is displaying an error message5202 alerting a user that the data entry field identifying the desirednumber of turns is outside of acceptable design parameters. In such aninstance, upon dismissal of the error message 5202 by the user, theidentified data field entry may be returned to a previous or defaultvalue within acceptable design parameters. As described, validation isperformed at an individual data entry field level.

With reference to FIG. 53, there is illustrated an instance of an errormessage according to another exemplary and non-limiting embodiment. Inthe example illustrated, user interface 5300 is displaying an errormessage 5302 alerting a user that the data entry field identifying thewire type is potentially inconsistent or incompatible with other datafield entries. Specifically, in the present example, error message 5302indicates that a selection of litz wire is inconsistent with the choiceof an operating frequency of 4000 kHz. In such embodiments, system 6400operates to warn users of poor choices for system parameters. Inaccordance with some exemplary embodiments, system 6400 may operate tosuggest alternative parameters choices and values resulting in adiminution of inconsistency. As described, such validation is performedat a panel level.

With reference to FIG. 54, there is illustrated an instance of an errormessage according to another exemplary and non-limiting embodiment. Inthe example illustrated, user interface 5400 is displaying an errormessage 5402 alerting a user that the geometry of the source coildefined by the data field entries is invalid. In such embodiments,system 6400 operates to warn users of design errors. As described, suchvalidation is performed at a tab level.

With continued reference to FIG. 47, at step 4706, the design parametersfor the resonator having been defined, the electromagnetic performanceof designed resonator may be modeled.

With reference to FIG. 55, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 5500 for computing andobserving predicted IMN results for the system 6400 defined in steps4702 and 4704. As illustrated, user-interface 5500 may be displayed inresponse to an activation of predicted IMN results tab 5502.

In accordance with exemplary and non-limiting embodiments, as describedabove, after predicting the electromagnetic performance of the system atstep 4706, impedance matching networks may be designed at step 4708.Then, at step 4710, the system thus modeled may be built and operationalparameters measured to be used as recursive inputs to step 4706 forfine-tuning and incrementally improving the design of the system.

In accordance with exemplary and non-limiting embodiments, thisfine-tuning may involve a validation procedure where source and devicecoil parameters are measured. These parameters may be then fed back intostep 4706 to calculate and/or re-calculate the matching circuitcomponents for any and/or all of the impedance matching networks. Theremaining process for assembling a wireless power system may involvepopulating actual components on source and device electronics boards andmeasuring resulting input impedances. Measured data from assembledcomponents may be then fed back into the system to finalize the matchingcomponent values for the optimum performance.

Proper design and construction of the impedance matching networks (IMN)on the source and device resonators may ensure safe and reliableoperation of the system over a range of source and deviceconfigurations. Typically, these configurations may involve a range ofdevice positions (with respect to the source), in which the device maybe under both nominal and open-circuit load conditions. In accordancewith exemplary embodiments, designed IMNs may ensure appropriate powerextraction from the source amplifier and the delivery of this power tothe device (without the need for active control) under all nominalconfigurations. When the device load is open-circuited (as is the casefor, e.g., a fully-charged battery), the source and device IMNs maytransform the open circuit in such a way as to minimize the power drawnfrom the source amplifier. In accordance with exemplary and non-limitingembodiments, the impedance matching networks may be designed so that themaximum open-circuited load voltage is less than any voltagelimitations, regulations, specifications, and the like, associated withany or all of the device electronic circuits and components.

With reference to FIG. 56, there is illustrated the steps of avalidation process according to an exemplary and non-limitingembodiment. First, at step 5602, source and device coil parameters suchas the quality factor, self-inductance, and coupling factor may bemeasured. Then, at step 5604, the measured coil parameters as well asamplifier and rectifier parameters may be fed into the system. Then, atstep 5606 electronic object design parameters such as the power supply,amplifier, rectifier, and device load parameters may be inserted intothe system. Next, at step 5608, a nominal device matching point for anacceptable coil-to-coil efficiency characteristic may be selected. Thenominal device matching point may chosen from a set values calculated ina parameter sweep and/or it may be entered by a user without consideringor having performed a parameter sweep. Next, at step 5610, a nominalsource matching point and a value for the source IMN for an acceptablepower characteristic and impedance to amplifier may be selected and/orcalculated. Then, at step 5612, the device IMN value may be selected foran acceptable output open-circuit voltage (or other systemspecification). Then, at step 5614, predictions of efficiency, power,voltages and currents at a certain operating point or as a function ofsweeping parameter may be observed. Then, at step 5616, amplifier andrectifier boards may be populated with calculated matching componentssuch as inductors, capacitors, switches, and the like, with thecalculated values, or with values close to the calculated values and theinput impedance measured. Lastly, at step 5618, the measured impedancevalues may be fed back into the system to adjust and finalize thematching component values.

With reference to FIG. 57, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 5700 for entering systemdesign parameters. As illustrated, user-interface 5700 may be displayedin response to an activation of system design tab 5702.

As illustrated, the left half of the user interface 5700 contains dataentry fields for Coil-to-Coil data—including the Q, L, and k values. Byclicking on the “Edit Values” button 5704, a table editor window mayappear, illustrated in FIG. 58, allowing one to input the measured Q, L,and k values determined from 5602. In the present example the sweepvalues are in SI units, e.g. units of meters are utilized fortranslation values.

In this exemplary embodiment, Terminal Objects refers to the electronicsattached to the power supply and load terminals. The design values forthe Source Electronics and Device Electronics may be modified via theillustrated user interface elements. In the present example, theseinclude specifications for the source-side power supply bus voltage andamplifier type (full-bridge switching amplifier, half-bridge switchingamplifier, etc.), and the device side rectifier type (full-bridge,half-bridge, etc.) and load characteristics (resistance, open-circuitedvoltage, etc.).

On the right half of user interface 5700 is a panel 5706 labeled “SelectNominal Matching Point for Device”. Panel 5704 may be utilized toperform the first step of designing the impedance matching network. Inan exemplary embodiment, this step may involve picking a nominalmatching point for the device which fixes the value of Z_(device) asillustrated. The design criterion to pay attention to in this step maybe the coil-to-coil efficiency. The first plot 5708 in panel 5706 showsthe ideal coil-to-coil efficiency, which is reached when Z_(device) isallowed to vary as a function of position, and the second plot 5710shows the maximum possible coil-to-coil efficiency with a fixedZ_(device). In some exemplary embodiments, the system may have a fixedZ_(device).

The nominal matching point may be changed by clicking on the “NominalMatching Point” spinner below panel 5706. As the nominal matching pointis changed, the second plot 5710 may change in real-time, near realtime, or as a result of activating a button or command. If the impedancematching networks are fixed, the software tool may suggest an impedancematching network that results in a system efficiency that is closest tothe calculated coil-to-coil efficiency and the specified nominalmatching point. That is, the second plot 5710 may be closest to thefirst plot 5708 at the nominal matching point, but may deviate more fromthe first plot 5708 at other points. Note that coil-to-coil efficienciesdisplayed on different tabs and/or reported at different stages in thedesign process may not reflect the electronics and components lossesassociated with the amplifier and rectifier designs, and therefore, thefinal end-to-end efficiency will be lower than the second plot 5710.

By reviewing the predicted performance of the system designed forvarious nominal matching points, the user may then select the nominalmatching point that yields an acceptable coil-to-coil efficiency profileacross the entire range of sweeping parameters. Final selections ofdesign parameters may be entered into the software modeling tool bysaving the parameters by any known method, including, for example,clicking on an “Accept Change” button which may be programmed to enterthe selected values into the system. If needed, the parameters inTerminal Objects may be adjusted until the changes are successfullyaccepted.

Nominal values display 5712 may be a display of the nominal values forthe device parameters, including the values of R_(surrogate) andC_(surrogate). These may be the actual component values to be used tosupport construction of the source IMN. That is, the surrogate valuesare not the final device IMN values, but rather a network that may beused to support accurate and efficient assembly of the sourceelectronics and impedance matching networks. The device IMN may bedesigned in another tab, or section of code, and may be reported to theuser once a source has been assembled and characterized. In embodiments,the device IMN may be calculated and reported at the same time as thesource IMN, and both the source and device may be assembled without theintermediate step involving surrogate circuits.

With reference to FIG. 59, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 5900 for performing a stepin determining and/or assembling an impedance matching network. Asillustrated, user-interface 5900 may be displayed in response to anactivation of source matching design tab 5902. In accordance withexemplary embodiments, after this step, a source design may be becomplete. In some assembly steps, coil-to-coil efficiency may be used asa design criterion. In other assembly steps, power flow may be used as adesign criterion. In exemplary embodiments, source impedance matchingnetwork design and assembly methods, results, techniques, and the like,may utilize power flow as a metric of design and assembly quality and/orsuitability.

In the top left panel 5904 are plotted two curves. First curve 5906 isthe predicted power output from the amplifier and second curve 5908 thepredicted power delivered to the device load. Below panel 5904 are threedata-entry fields under Source Matching Inputs. One may utilize theup/down arrows on the spinner controls to the right of the data-entryfields to adjust their values.

In accordance with an exemplary and non-limiting embodiment, an exampledesign sequence is as follows. First, the nominal matching point for thesource is selected by pressing the up/down arrows on the nominalmatching point spinner. At this nominal point, a fixed output power isextracted from the amplifier. This point may be moved to the center ofthe desired output range.

Next, the nominal output power may be selected by pressing the up/downarrows on the nominal output power spinner. This determines the poweroutput from the amplifier at the nominal matching point from theprevious step. This value may be increased to ensure enough power isdelivered to the load over the desired operating range. While thisadjustment may change the shape of the overall power delivery curve, thepower delivery curve may be readjusted in the next step.

Finally, the reactance value for X3 in the source IMN may be set bypressing the up/down arrows on the X3 slider. This will adjust the shapeof the power delivery curve. The value of X3 may be changed so that thecurve is approximately symmetric about the nominal matching point. Inaccordance with exemplary embodiments, there may be two solutions withacceptable curves, one with a positive X3 (an inductor), and one with anegative X3 (a capacitor).

As illustrated, the computed source IMN components appear in panel 5910below the controls. The components may be inspected to determine if theyare acceptable for the intended application. If acceptable, clicking onthe “Accept Changes” button will accept all changes for storage on thesystem. If the values are not acceptable, then the user should return tothe previous steps and select different parameters for the system designuntil a suitable and/or acceptable impedance matching network has beendesigned by the tool.

Panel 5912 displays the impedance presented to the amplifier, as well ascomponent currents and voltages for verification that all values arewithin acceptable ranges (e.g., that voltage levels are within componenttolerances). At this point, one may go back and adjust the nominalmatching point, the nominal power output, and/or the X3 spinners if thecomponents are determined to be unacceptable for the intendedapplication.

Having set the nominal matching point (coil-to-coil configuration) anddetermined the source IMN components, a value of X3 may be selected forthe device IMN, which will fully determine the device IMN components.The design criterion here may be the open-circuit voltage across theload terminal on the device. This parameter may be important when, forexample, the load is a DC/DC converter with a maximum input voltagetolerance.

With reference to FIG. 60, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 6000 for performing a nextstep in impedance matching. As illustrated, user-interface 6000 may bedisplayed in response to an activation of device matching design tab6002. Panel 6004 plots the nominal load voltage 6006 and theopen-circuit load voltage 6008, as a function of the sweeping parameter.Below panel 6004 is a control for adjusting the device X3 and optimizinganother design criterion—the open circuit voltage. Varying the device X3may change the open-circuit voltage profile, without changing thenominal load voltage profile. The open circuit voltage is what appearsat the load terminals if, for example, the load is a battery chargerthat has finished charging a battery. X3 may be varied, for example, byclicking on the spinner arrows until an open-circuit voltage profile hasbeen obtained. When the value of X3 is set, the device IMN componentsare displayed in panel 6010. If X3 is a positive reactance, L3 will benon-zero and C3 will be infinite (short circuited). If X3 is negative,C3 will be finite and L3 will be zero.

After deciding on a value for X3, panel 6012 displays device componentcurrents, voltages, and power dissipation to ensure that all quantitiesare within the component tolerances.

With reference to FIG. 61, there is illustrated an exemplary andnon-limiting embodiment of a user-interface 6100 for displaying computedsource and device IMN component values. As illustrated, user-interface6100 is displayed in response to an activation of predicted end-to-endresults tab 6102. Panel 6104 displays the computed source and device IMNcomponent values. Panel 6106 displays plots of a range of physicallyrelevant quantities, including the currents and voltages from theprevious tabs. Also included is the end-to-end efficiency prediction forthe system, including losses in the electronics. These predictions maybe checked before proceeding to verify that all predicted quantities liewithin an acceptable range.

In accordance with exemplary and non-limiting embodiments, the systemoperates to guide one through the process of physically constructing thesource-and device-side IMNs. As both follow a similar workflow, both thesource matching user interface and the device matching user interfaceare described more fully below with reference to source matching userinterface 6200. With reference to FIG. 62, there is illustrated anexemplary and non-limiting embodiment of a source matchinguser-interface 6200. As illustrated, user-interface 6200 is displayed inresponse to an activation of source matching tab 6202.

As described more fully with references to exemplary and non-limitingembodiments of device and source build user interfaces below, initialand target impedances are shown in the “Matching Targets” panel on theleft. The source IMN will transform Z_(initial)=R_(initial)+jX_(initial)to Z_(final)=R_(final)+jX_(final). Z_(initial) refers to the impedanceon the coil side of the “T” IMN. Z_(final) refers to the impedance thatshould be seen from the terminal—either by the amplifier for the sourceside and or by the load for the device side.

Each user interface 6200 is designed to show the ideal or near idealmatching components determined in the previous tabs and to compare themto measured values of as-built components as they are soldered in.

For example, the calculated source IMN components from the SourceMatching user interface 5900 are displayed on the left side in the“Calculate Ideal Matching Network” panel 6204. There are additionalcontrols that allow one to vary component values and recalculate thematch. This is useful, for example, if the inductance of the L3 inductorin inventory is larger than the predicted ideal component value. Byactivating the check-boxes for C2 and C3 to be free parameters, thematch may be recalculated. This will result in a finite value of C3 thattrims out the excess reactance from L3. Users may utilize such a featureto customize the IMN as desired (e.g., by reducing sensitivity tovariations in certain component values).

On each user interface 6200, a Smith Chart 6206 illustrates thetrajectory the impedance takes as components are successively populated.Starting from the initial impedance Z_(initial) at the top of the SmithChart 6206, as the reactance associated with C1 becomes more negative(increasing C1), the impedance traces out the curve to the end-pointlabeled C1. As the admittance associated with C2 increases (increasingC2), the resulting impedance traces out the dark blue curve. If L3 werenon-zero, the impedance would trace out a green curve. Finally, as C3 'sreactance becomes more negative (decreasing C3), the net impedance seenfrom the terminal traces out the red curve. By viewing how the traceschange as components of the ideal or near-ideal IMN vary, one can buildintuition about the behavior and sensitivity of each component.

As described more fully below, “As-built Matching Network” panel 6208allows one to track the effective value of components soldered into theIMN. Solder pads and traces may have some parasitic capacitances andinductances, and capacitor values may not be exactly equal to theirlisted value. Variations of a few percent can cause significantdeviations in the IMN behavior, as can be seen by changing the values ofthe “Ideal IMN” components.

The As-Built panel 6208 may be utilized as follows: beside eachcomponent value is a field showing what the impedance at the componentis given its current value and the value of the other downstream(towards the source coil) components. The value of the current componentmay be adjusted until the displayed impedance matches as closely aspossible the value measured from the network analyzer, or any equivalentmeasurement equipment. The component value thus displayed is the actualcomponent value on the board, including parasitics and natural componentvalue variation. The far right text field on this row displays theamount to add/subtract in order to get to the desired IMN value.

In embodiments, when soldering capacitors into the impedance matchingnetworks, it may be preferable to start by soldering in a component witha specified value equal to approximately 80% of the desired value. Then,once the effective capacitor value is deduced using the as-built userinterface, the remaining value can be added. This technique may reducethe amount of times a capacitor needs to be unsoldered from the networkand replaced with a different one. If soldering and unsolderingcapacitors are equally desirable or undesirable, there may not be a needto initially solder in lower capacitance components. Using the matchingtool in this way enables the user to construct the matching network tohigh accuracy.

With reference to FIG. 63, there is illustrated a block diagram of asystem 6300 for practicing various exemplary and non-limitingembodiments of the software modeling tool described above. A computingdevice 6302, including, but not limited to, a personal computer, server,PDA and the like comprises a processor 6304 and attendant memory 6306.Processor 6304 may be enabled to execute software instructions such asmay be stored in a computer readable medium such as, for example, memory6306, to perform the software steps described above. User interface 6308enables the entry of data and information, such as from a user, and thedisplay of information to a user.

In accordance with other exemplary and non-limiting embodiments a designand modeling tool may be used to assist a designer in developing awireless energy transfer system, from initial concept to final test. Aflow chart depicting the main steps of the design and modeling tool isshown in FIG. 64. The main steps of the design tool are as follows.

Initially, a designer may pick inputs such as frequency, power, coilgeometry, and other parameters that are suited for an application.

Next, the choice of a type of resonator coils (shielded or unshielded)may be determined by whether or not extraneous conductors are nearby.Extraneous objects may be susceptible to parasitic eddy currents thatmay reduce the Q of one or both resonators. A shielded resonator coilmay typically be preferable near extraneous conductors, but may beslightly larger than an unshielded resonator coil of a similar surfacearea. In other applications, the choice of resonators may be betweenapproximately planar coils and three-dimensional coils, such as a helixand the like. Helical coils may have increased alignment tolerance butcould be more difficult to package.

Next, frequency considerations and choices such as resonator conductorchoices may be made in the modeling tool. For example, Litz wire may bechosen as the conducting material because it works well below the AMradio band (<520 kHz) and solid core wire may be chosen where it maywork better, such as at higher frequencies (e.g. the ISM bands at 6.78and 13.56 MHz).

Next, the highest Qs and coupling coefficients may be calculated forvarious coil designs. A few iterations may be utilized to study howdifferent coil parameters affect Q and coupling (k) over a sweptparameter range, such as distance between coils.

Next, once acceptable coupling between coils is realized, the designermay pick a nominal value of the sweep parameter (e.g. distance) tocalculate the optimum IMNs (Impedance Matching Networks) to couple theresonators to the source and device electronics. If the chosen nominalvalue is a distance, that distance will correspond to a nominal value ofcoupling coefficient k.

Next, the designer may calculate a power-transfer curve plotted as afunction of the sweep parameter. In many cases, a fixed-tuned amplifiermay provide adequate performance. In some cases, an auto-tuned amplifierand/or rectifier that can dynamically change the IMN may provideextended performance over the sweep parameter.

Then, in the lab, the designer may attach the IMN components ontoinductive elements or coils and make a few measurements on a networkanalyzer, oscilloscope, and the like to fine-tune the parameters in thesimulator. The user may build and test the system and compare themeasurements to the simulation output. After one or two iterations, theuser may make small adjustments to capacitors, inductors, and the like,or to simulation parameters to improve the agreement between thesimulation and measurements.

Lastly, the source and device resonators may be packaged and go throughfinal testing. The designer may use the simulator and the modeling toolto provide what-if analyses. For example, what is the expected toleranceof the system to orientation variations? Or, how much worse is theefficiency at another distance?

While the invention has been described in connection with certainpreferred embodiments, other embodiments will be understood by one ofordinary skill in the art and are intended to fall within the scope ofthis disclosure, which is to be interpreted in the broadest senseallowable by law.

All documents referenced herein are hereby incorporated by reference intheir entirety as if fully set forth herein.

1.-22. (canceled)
 23. A computer-implemented method for designing awireless power transfer system, the method comprising: through acomputer-implemented user interface: defining one or more attributes ofa source resonator and a device resonator forming the wireless powertransfer system; defining a relative position and orientation betweenthe source resonator and the device resonator, wherein the relativeposition is defined in three-dimensional coordinates; and defining arange of a sweep parameter which determine conditions of the wirelesspower transfer system; calculating, using a processor, anelectromagnetic performance of the wireless energy transfer system forthe conditions determined by the range of the sweep parameter; andgenerating, through the computer-implemented user interface, a visualrepresentation of information about the modeled electromagneticperformance of the wireless energy transfer system based on the range ofthe sweep parameter.
 24. The method of claim 1 further comprising:defining, through the computer-implemented user interface, an impedancematching network of the wireless power transfer system; whereincalculating the electromagnetic performance is based on the systemincluding the impedance matching network.
 25. The method of claim 24,wherein the impedance matching network is electrically connected to thesource resonator or the device resonator.
 26. The method of claim 23wherein the information about the modeled electromagnetic performance isselected from the group consisting of a power transfer efficiency, apower to a device terminal, an impedance of the system and a voltage ofthe system.
 27. The method of claim 23 wherein the sweep parameter is aseparation distance between the source resonator and the deviceresonator.
 28. The method of claim 23 further comprising definingadditional sweep parameters which determine the conditions of thewireless power transfer system.
 29. The method of claim 23 wherein: theone or more attributes of the source resonator comprises at least onesource resonator parameter selected from the group consisting of sourceresonator wire type, source resonator length, source resonator width,source resonator coil winding direction, source resonator coil number ofturns and source resonator coil spacing between turns; and the one ormore attributes of the device resonator comprises at least one deviceresonator parameter selected from the group consisting of deviceresonator wire type, device resonator length, device resonator width,device resonator coil winding direction, device resonator coil number ofturns and device resonator coil spacing between turns.
 30. The method ofclaim 23 wherein: the computer-implemented user interface provides avisual representation of the source resonator or the device resonator;the visual representation of the source resonator or the deviceresonator is updated in real-time to reflect changes of the one or moreattributes of the source resonator and the device resonator definedthrough the computer-implemented user interface.
 31. The method of claim23 further comprising searching, through the computer-implementedinterface, a database based on a search criteria to select the one ormore attributes of the source resonator and the device resonator. 32.The method of claim 23 wherein defining one or more attributes of thesource resonator and the device resonator comprises retrieving a designof the source resonator or the device resonator saved in a library. 33.The method of claim 32 wherein the library includes multiple groups ofdesigns of coils which are categorized based on attributes of thedesigns including frequency characteristics of the designs.
 34. Anon-transitory computer-readable medium containing a set of instructionsthat causes a computer to: enable the defining through acomputer-implemented user interface of one or more attributes of asource resonator and a device resonator forming a wireless energytransfer system; enable the defining through the user interface of arelative position and orientation between the source resonator and thedevice resonator, wherein the relative position is defined inthree-dimensional coordinates; enable the defining through the userinterface a range of a sweep parameter which determine conditions of thewireless power transfer system; calculate an electromagnetic performanceof the wireless energy transfer system for the conditions determined bythe range of the sweep parameter; and generate a visual representationof information about the modeled electromagnetic performance of thewireless energy transfer system based on the range of the sweepparameter.
 35. The computer-readable medium of claim 34 further causesthe computer to: enable the defining through the user interface animpedance matching network of the wireless power transfer system;wherein calculation of the electromagnetic performance is based on thesystem including the impedance matching network.
 36. Thecomputer-readable medium of claim 35 wherein the impedance matchingnetwork is electrically connected to the source resonator or the deviceresonator.
 37. The method of claim 23 wherein the information about themodeled electromagnetic performance is selected from the groupconsisting of a power transfer efficiency, a power to a device terminal,an impedance of the system and a voltage of the system.
 38. Thecomputer-readable medium of claim 34 wherein the sweep parameter is aseparation distance between the source resonator and the deviceresonator.
 39. The computer-readable medium of claim 34 further causesthe computer to enable the defining through the user interfaceadditional sweep parameters which determine the conditions of thewireless power transfer system.
 40. The computer-readable medium ofclaim 34 wherein: the one or more attributes of the source resonatorcomprises at least one source resonator parameter selected from thegroup consisting of source resonator wire type, source resonator length,source resonator width, source resonator coil winding direction, sourceresonator coil number of turns and source resonator coil spacing betweenturns; and the one or more attributes of the device resonator comprisesat least one device resonator parameter selected from the groupconsisting of device resonator wire type, device resonator length,device resonator width, device resonator coil winding direction, deviceresonator coil number of turns and device resonator coil spacing betweenturns.
 41. The computer-readable medium of claim 34 wherein: thecomputer-implemented user interface provides a visual representation ofthe source resonator or the device resonator; the visual representationof the source resonator or the device resonator is updated in real-timeto reflect changes of the one or more attributes of the source resonatorand the device resonator defined through the computer-implemented userinterface.
 42. The computer-readable medium of claim 34 further causesthe computer to search a database based on a search criteria forselecting the one or more attributes of the source resonator and thedevice resonator.
 43. The computer-readable medium of claim 34 whereinthe defining one or more attributes of the source resonator and thedevice resonator comprises retrieving a design of the source resonatoror the device resonator saved in a library.
 44. The computer-readablemedium of claim 43 wherein the library includes multiple groups ofdesigns of coils which are categorized based on attributes of thedesigns including frequency characteristics of the designs.